May I join..? 
I can provide information about Javanese. I personally don't like to call Javanese civilization as Majapahit, because Majapahit itself is a kingdom, not a civ..
Javanese Civilization encompassing all Sundanese and Javanese (Java Island), Madurese (Madura Island), and Balinese (Bali Island). Also, its influence spread across Maritime Southeast Asia.
Here we go..
Javanese
History
Java is an island in Maritime Southeast Asia. This island is "blessed" with tropical climate and chain of volcanoes. Rainfall allowed the development of wet-field rice cultivation. More mountains and highlands help to split the interior into a series of relatively isolated regions suitable for wet-rice cultivation; volcanic ash and lava also form rich soil. The rice lands of Java are among the richest in the world.
Yes indeed, the first Javanese civilization was emerged based on agriculture. The island allowed the development of wet-field rice cultivation, which required sophisticated levels of cooperation between villages. Out of these village alliances, small kingdoms developed.
Yawadvipa or Jawa Dwipa (Java Island) was mentioned in India's earliest epic, the Ramayana. The first historically recorded Indianized kingdom in Western Java is Salakanegara, created by Indian trader after marrying a local Sundanese princess. This Kingdom existed between 200-362 AD.
After that, many recorded kingdoms was emerged. From Taruma, Sunda, Kalingga, Medang (The one who build Candi Borobudur and Prambanan), Kediri, Singhasari, Wilwatikta (The official name of Majapahit that time), Demak (The first major sultanate in Java), Pajang, Mataram, to Surakarta and Yogyakarta which integrated with Indonesia today.
Although Javanese kingdoms mainly dependent on rice agriculture, yet they also pursued trade within the Indonesian archipelago, and with China and Indian.
In the era of Kediri, their economy grew to rely more heavily on trade, especially the spice trade. This resulted from Kediri development of a navy, giving them the opportunity to control the spice trade routes to eastern islands. Kediri collected spices from tributaries in southern Kalimantan and the Maluku Islands. Indians and Southeast Asians then transported the spices to Mediterranean and Chinese markets by way of the Spice Route that linked a chain of ports from the Indian Ocean to southern China.
The peak of Javanese thalassocracy (from Greek language, literally "rule of the sea") was during the era of Majapahit, the greatest empire in Java. Majapahit was a vast thalassocratic archipelagic (ruling the island group and sea) empire from 1293 to around 1500. Majapahit was an empire of 98 tributaries, stretching from Sumatra to New Guinea; consisting of present day Indonesia, Singapore, Malaysia, Brunei, southern Thailand, the Philippines, and East Timor. Also controlling the Spice Route and spice islands in East Indonesian Archipelago and Maritime Silk Route in Malacca Strait.
This is the result of Gajah Mada's effort, the prime minister of Majapahit, to fulfilled his famous Palapa Oath during reign of Queen Tribhuwana (Yay.. My Favorite Empress..
If Firaxis want to add Javanese, I hope they choose her and dressed her like this..
) .
For protecting their hegemony, Majapahit rigidly use fire-arms and cannonade as a feature of warfare. The Javanese bronze breech-loaded swivel-gun, more correctly known as a cetbang was used ubiquitously by the Majapahit navy.
Majapahit navy and later Javanese kingdoms also use jong ship, a large ship with three or four screens. The entire hull was built without using nails. Mentioned by Portuguese at Demak era, Javanese jong has four masts, made of four layered board and able to withstand cannon fire Portuguese ships. The weight average jung 600 tons, surpassing the Portuguese warships. Jong bulk's weight reached 1,000 tons are used as troop carriers.
After the decline of Majapahit, Javanese began to face the rise of Javanese Sultanates (1475 - 1800), the European colonization (1800 - 1942), the Japanese occupation (1942 - 1945), until the emergence of Indonesia (1945 - now). Right now, Java is the world's most populous island, and one of the most densely-populated places on the globe. Java is the home of 60 percent of the Indonesian population. Java dominates Indonesia politically, economically and culturally.
Religion
Today the majority of the Javanese people identify themselves as Muslims. Because Javanese civilization has been influenced by more than a millennia of interactions between Kejawen or Sunda Wiwitan (the native animism) and the Indian Hindu—Buddhist culture, there are traces of their influences in Javanese history, culture, traditions and art forms. In the end, majority of Javanese follow an unique syncretic form of Islam, Hinduism, Buddhism and Kejawen.
Language
Javanese Language is a member of the Austronesian family of languages and is closely related to, but distinct from, other languages of Indonesia. It is notable for its great number of nearly ubiquitous Sanskrit loans, found especially in literary Javanese. This is due to the long history of Hindu and Buddhist influences in Java.
The Javanese language was commonly written with the a script descended from the Brahmi script, natively known as Hanacaraka or Carakan.
Music
The most famous Javanese music is gamelan, a traditional musical featuring a variety of instruments such as metallophones, xylophones, kendang (drums) and gongs; bamboo flutes, bowed and plucked strings. Vocalists may also be included.
Architecture
Candi is the one remarkable building in Java. In modern Indonesian, the term Candi commonly refers to ancient Hindu-Buddhist temples.
The term "candi" itself derived from Candika one of the manifestations of the goddess Durga as the goddess of death. This suggested in ancient Java the "candi" has mortuary function as well as attributed with the afterlife. The historians suggested that temples of ancient Java also used to store the ashes of cremated deceased kings or royalties.
This is also in-line with buddhist concept of stupa as the structure to store buddhist relicts including the ashes and remnants of holy buddhist priest or the buddhist king, the patron of buddhism. The statue of god stored inside the garbhagriha (main chamber) of the temple often modelled after the deceased king and considered as deified self of the king portrayed as Vishnu or Shiva according to the concept of devaraja.
The another architecture is pendopo and joglo. Joglo is a traditional vernacular house of Javanese people. It consist of two parts; the pendopo and dalem. The pendopo is the front section of Joglo that have large roofed space with columns and without wall or partition. The dalem is the inner sections with walled enclosure and rooms such as bedroom and kitchen.
Pendopo are common ritual spaces primarily intended for ceremony, wayang theater, and also for a variety of purposes such as receiving guests in the compounds of wealthy Javanese, and even as cottage industry work spaces.
Cultural Heritage Elements
Javanese already have four cultural elements that was listed in UNESCO Intangible Cultural Heritage:
- Wayang Theater, an unique form of theatre employing light and shadow. The puppets are crafted from buffalo hide and mounted on bamboo sticks. When held up behind a piece of white cloth, with an electric bulb or an oil lamp as the light source, shadows are cast on the screen. The plays are invariably based on romantic tales, especially adaptations of the classic Indian epics, the Mahabharata and the Ramayana. Some of the plays are also based on local happening or other local secular stories. Islam missionaries also often to add Islamic element into Indian epic, resulting culture and religion syncretisme.
- Kris, an asymmetrical dagger famous for its distinctive wavy blade, but in the past, most had straight blades.
- Batik, a cloth that is traditionally made using a manual wax-resist dyeing technique. Javanese traditional batik, especially from Yogyakarta and Surakarta, has notable meanings rooted to the Javanese conceptualization of the universe. Traditional colours include indigo, dark brown, and white, which represent the three major Hindu Gods (Brahma, Vishnu, and Shiva). This is related to the fact that natural dyes are most commonly available in indigo and brown. Certain patterns can only be worn by nobility; traditionally, wider stripes or wavy lines of greater width indicated higher rank. Consequently, during Javanese ceremonies, one could determine the royal lineage of a person by the cloth he or she was wearing.
- Angklung, a musical instrument made of two bamboo tubes attached to a bamboo frame. The tubes are carved to have a resonant pitch when struck and are tuned to octaves. The base of the frame is held in one hand, whilst the other hand struck the instrument. This causes a repeating note to sound. Each of three or more performers in an angklung ensemble play just one note or more, but altogether complete melodies are produced. The Angklung is popular throughout Southeast Asia, but it originated in today's Java and has been played by the Sundanese for many centuries.
Cultural Heritage Sites
Javanese also have three Cultural Heritage Sites that was listed in UNESCO World Heritage Sites. The list is:
- Borobudur Temple Compounds, a term used by the World Heritage designation of the area of three Buddhist candi in Central Java, Indonesia. It comprises Borobudur, Mendut, and Pawon. These three candis are located in a straight line, and have been considered as being built during the Sailendra dynasty from Medang Kingdom circa 8th–9th centuries. Borobudur itself is the largest Buddhist structure in the world.
- Prambanan Temple Compounds, a 9th-century Hindu candi compound in Central Java, Indonesia, dedicated to the Trimurti, the expression of God as the Creator (Brahma), the Sustainer (Vishnu) and the Destroyer (Shiva). The candi compound is located approximately 18 kilometres (11 mi) east of the city of Yogyakarta on the boundary between Central Java and Yogyakarta provinces. The candi, is the largest Hindu candi in Indonesia, and is one of the largest Hindu temples in Southeast Asia.
- Subak System, Subak is the name of water management (irrigation) system for rice terraces on Bali island, Indonesia. For Balinese, irrigation is not simply providing water for the plant's roots, but water is used to construct a complex, pulsed artificial ecosystem. Rice terraces in Bali were built around water pura (Balinese temple) and the allocation of water is made by a priest.
Event and Trivia
Devaraja
"Devaraja" is the Hindu-Buddhist cult of deified royalty in Southeast Asia. It could be simply described as Southeast Asian concept of divine king. The concept viewed the monarch to possess transcendental quality, the king as the living god on earth, the incarnation of the supreme god, often attributed to Shiva or Vishnu. The concept was institutionalized and gain its elaborate manifestations in ancient Java and Cambodia, where monuments such as Prambanan and Angkor Wat were erected to celebrate the king's divine rule on earth.
The cult of devaraja or God King was the ancient Cambodian state religion, while it may have originated in Java. In ancient Java, since Sailendra dynasty, or even older Tarumanagara kingdom, the state religion regarded the king as god incarnated on earth.
Jayavarman II that was widely regarded as the king that set the foundation of Angkor period in Cambodian history, began with the ritual conducted to celebrate the independence of Khmer from Javanese dominion. At that ceremony Prince Jayavarman II was proclaimed a universal monarch or God King (Deva Raja in Sanskrit). According to some sources, Jayavarman II had resided for some time in Java during the reign of Sailendras Dynasty, or "The Lords of Mountains" Dynasty, from Medang Kingdom, hence the concept of Devaraja or God King was imported from Java. At that time, Sailendras allegedly ruled over Java, Sumatra, the Malay Peninsula and parts of Cambodia.
Prophecies of Jayabaya
Sri Mapanji Jayabaya or Jayabaya, was Javanese King of the Kediri in East Java from AD 1135 to 1157. Jayabaya is most famous for his oracles or prophesies attributed to him. Jayabaya is attributed as author of the Prelambang Joyoboyo, a prophetic book that played an important role in the Japanese occupation.
According to a selectively lines within a Jayabaya prophesy (all are extremely long epic poems):
"The Javanese would be ruled by whites for 3 centuries and by yellow dwarfs for the life span of a maize plant prior to the return of the Ratu Adil (Just King): whose name must contain at least one syllable of the Javanese Noto Negoro."
When Japan occupied the Netherlands East Indies, in the first weeks of 1942, Indonesians danced in the streets, welcoming the Japanese army as the fulfillment of the prophecy ascribed to Jayabaya, who foretold the day when white men would one day establish their rule on Java and tyrannize the people for many years – but they would be driven out by the arrival of yellow men from the north. These yellow dwarves, Jayabaya had predicted, would remain for one crop cycle, and after that Java would be freed from foreign domination. To most of the Javanese, Japan was a liberator: the prophecy had been fulfilled.
In the waning days of 1944, Japan realized that they could not win the World War II. The Japanese officially granted Indonesia its independence on 9 August 1945. As one account of Indonesian history puts it, "With the minor exception that three crops had been harvested, Jayabaya's prophecy had been realized."
Many believe that the time for the arrival of a new Ratu Adil is near (as the prophecies put it, "when iron wagons could drive without horses and ships could sail through the sky"), and that he will come to rescue and reunite Indonesia after an acute crisis, ushering in the dawn of a new golden age.
Mongol invasion of Java and the founding of Majapahit
Kertanegara, the fifth ruler of Javanese Kingdom of Singhasari, was a man with ambition. In 1289, Mongol emissary came to Java to demand his submission to the Great Khan of the Yuan dynasty, Kublai Khan. Kertanegara reject it, cut their ears and send them back to China. The Khan was shocked and ordered a punitive expedition against Kertanagara. Anticipating Mongolian revenge, he preparing to thwart the forthcoming invasion by conquering important ports and kingdoms in Maritime Southeast Asia. His most important expedition was Pamalayu expedition to Sumatra in 1292, where he send Javanese army to conquer Sumatra from various successor states of Srivijaya.
When the bulk of Javanese army in overseas, Jayakatwang, viceroy of Kediri, a vassal state of Singhasari, seize his chance and launched the coup against Singhasari. He launched diversionary attack to the northern Java, where his troops draw the remaining Singhasari troops left in the island that was lead by Kertanegara's son-in-law, Raden Wijaya. With Singhasari defenseless he attack the capital city.
Kertanegara was killed along with many courtiers in his palace, apparently when they were drinking palm wine in a religious Tantric Buddhism ceremony. Jayakatwang then declare himself ruler of Java and king of the restored Kediri.
Among few surviving relatives of Kertanegara was Raden Wijaya, who fled to Madura where he was sheltered by its regent, Arya Wiraraja. Following Wiraraja plea, Jayakatwang forgive Wijaya, who in return submitting himself to Jayakatwang. Jayakatwang gave Wijaya land in Tarik forest in Brantas delta, to build a village that was later called Majapahit, from the sour (pahit) beal (maja) tree that grow in the area.
Mongol expedition of the Yuan dynasty sent by Kublai Khan finally arrived in Java. Sailing from Quanzhou, and after journey from China through Dai Viet and Champa, landing at the port of Tuban, Java in early 1293. Raden Wijaya seeing this event as opportunity to revenge Kertanegara's death and claim the throne of Java. He soon offered submission and allied himself with the Mongol, who wasn't aware on the recent political change in Java.
The Mongolian expedition consisted of 20.000 army with 1.000 boats and a year of grain provision. The expedition consisted mostly of southern Chinese conscript. They arrived at port of Tuban and soon preparing their fleet to enter the rivers of Java.
With Wijaya as guide, Mongol troop declared war against Jayakatwang. Wijaya's and his Mongol allies defeated captured Jayaktwang's navy in Surabaya at delta of Brantas river. Following the victory they easily marched along Brantas to Kediri in Java's interior. After heavy fight, they besieged and conquered Kediri. Jayakatwang was captured and then executed, in March 1293.
Thus the troops sent to Java that with the intention to punish the king who insulted the Mongols (Kertanegara), ended up revenging his death and killing his usurper (Jayakatwang). 
Once Jayakatwang was destroyed by the Mongols, Raden Wijaya returned to Majapahit, ostensibly to prepare his tribute settlement, leaving his allies who were exhausted after the war with Jayakatwang to celebrate their victory. Wijaya asked the Yuan forces to come to his country unarmed.
Two hundred unarmed Yuan soldiers led by two officers were sent to Raden Wijaya's country, but Raden Wijaya quickly mobilized his forces again and ambushed the Yuan convoy. After that Raden Wijaya marched his forces to the main Yuan camp and launched a surprise attack, killing many and sending the rest running back to their ships. The Yuan forces had to withdraw in confusion, as the monsoon winds to carry them home would soon end, leaving them to wait on a hostile island for six months. The Yuan army lost more than 3,000 of its elite soldiers.
===
Ack.., my post is more like wiki than history school..
But well.. Whatever..