Remember in the Beyond the Sword expansion pack of Civ 4, how the units and buildings of each civilization looked unique to their cultural region/continent? Like if you were Aztec, your units would look like Native Americans, and if you were Roman, your units would like Mediterranean? That was probably my favourite feature of that expansion pack (although they could have gone a little further, making Archers and your first gunpowder units culturally unique as well), and I would really like to see this in Civilization 5. They good news is that the Settlers do look culturally unique already, so it may well be a feature that will be added, but still I'd like to know...will they make your units and buildings culturally unique to your civ's region?
So far this is the amount of civs to each cultural region/continent so far (and it refers to the people's culture, not always where they live. For example, American civ lives in America, but has a European culture, not Native American):
Middle East - 5 (Babylon will make it 6)
Asia - 3
Africa - 1
Mediterranean - 2
Europe - 5
Americas - 2
Polynesia - 0
With this unbalance of cultural areas, they should also consider adding important and worthy civs from some of those areas.
Middle East is fine at 6, but wouldn't be complete without Assyria (the only World Power of history that hasn't appeared in the game), making it 7.
Asia could use Mongolia, Korea and Majahahit to make it 6.
Africa could use Ethiopia, Zululand or Bantu to make it 3.
Mediterranean could use Spain, Phoenicia or Carthage to make it 4.
Europe is fine at 5, but wouldn't be complete without the Norse, making it 6.
Americas could use Inca, Maya and Sioux to make it 5.
Polynesia (if considered), could use Moari, Papuan and Rapa Nui to make it 3.
This would insure a well balanced cultural world.