BOZ said:
at least separate the northern africans from the southern africans - very very different cultures there.
The difficulty with doing African cultures (and Asian cultures too, for that matter) is that there are so many of them. There are some 1000 spoken languages there besides those introduced by Europeans and Arabs. There are also numerous ethnic groups whose ancestral homelands do not neatly correspond to the way the map was redrawn in the colonial era. Trying to fit every single African into neat little categories won't really work. What would work is taking the dominant groups of each region and then explaining that there are indeed more, but more information is not yet available.
Geographically and culturally, the major divisions of Sub-Saharan Africa are: West Africa, East Africa, and Central Africa. Southern Africa may be an interesting conglomeration of all three, but I'm not certain of that. Now, depending upon whose perspective you use when naming the areas in what would be Sub-Saharan Africa, you may want to use the people's names for themselves and their homelands or use the names created by foreigners for them. You can take a cue from foreign languages and name the continent Bantu (meaning "[the] people"), which is the dominant linguistic group in Africa (though splintered and divided after millenia of migration and interaction with foreign peoples). Instead of naming the countries after their historical counterparts, perhaps naming them for the languages could work, although in many cases, I'd imagine that there would be some overlap. Besides the Bantu languages, there are also the Khoisan languages (from the Khoikhoi people). There are far too many of them to list and categorize here, so you would have to do some pruning if you want to make it manageable.
If you want to go completely fictional, you can steal the contry of Zamunda from
Coming to America.
The same thing can apply to Asian cultures as well. Instead of doing China and Japan as the great monoliths of East Asian culture, perhaps breaking them down and renaming them. China's name for itself is
Zhong guo, which means "middle land/kingdom." However, if you take some ideas from historical periods and ethnic groups in China, you can have something like
Ming guo ("bright land/kingdom," named after the Ming dynasty) or
Han guo ("Han kingdom/land," named after the Han, the dominant ethnic group in China). The same could go for Japan, Korea, and Southeast Asia.
I hope this helps.