Since we have three North African civilizations (Ptolemies, Carthaginians, and Kushites) already, I thought that one located entirely south of the Sahara would be welcome as well. So I am going to suggest the Nok culture that thrived in the area of Nigeria between 900 BC to 200 AD. There's not a lot we know about them, especially since they don't seem to have used a written script, but they have left behind numerous sculptures attesting to an artistic tradition that would influence those of later West African kingdoms.
Nok Culture on the World History Encyclopedia
Some choice Nok sculptures:
I don't think we know for sure what language the Nok people spoke, but I would use Yoruba or Ibo vocabulary for unit and building names since those are some of the cultures influenced by the Nok culture. Below are some images showing what these cultures looked like in more recent periods:
Yoruba palace compound (I think)
Yoruba house
Ibo house
Ibo warriors with armor
Ibo warriors with spears and shields
In addition, as part of this larger representation of West Africa, African rainforest animals could be added to the game. Game could include the bongo, guinea-fowl, okapi, gorilla, and forest elephants (which I believe are already in the game), whereas leopards and chimpanzees would be predators.
Bongo
Guinea-fowl
Okapi
Gorilla
Leopard
Chimpanzee