I agree, bombshoo. I think the amount of northern territory that Shiro suggests be included is a bit overmuch -- a lot of that is going to be Siberian tundra and the Gobi Desert, and/or places that in the real world that have little to no population or significance that could be translated into Civ terms.
As for the civs -- the Uighurs (I'm pretty damn sure that's the correct spelling, at least that's how I remember a professor of Chinese Language and Cultural Studies spelling it) ARE a Turkic people, so instead of including a "Turks" civ, stick with the Uighurs. Otherwise people will just think of modern/Ottoman Turkey. It doesn't matter too much whether you have have the Huns or the Xiong-Nu, since their of the same origin, but for a UU, instead of giving the same one as the Mongols (Keshik), they could have an earlier horse archer unit, since they used horse archers effectively at a much earlier date (almost 1000 years prior, I think) than the great conquests of the Mongols.