The Tamils (it took centuries for them to be absorbed in the greater India, and not all of the subcontinent employed camels for warfare.).
Many Swiss armies served as mercenaries during the medieval period, mostly for the Vatican City)
The Swiss (another significant civilization in Europe around the medieval time period, as it consisted of a confederation of city states.
Besides the "Ruins of Empires" scenario in the Portuguese campaigns have the Swahili people represented by the Malians and Ethiopians. The Swahili people didn't play a major role in this timeframe.
The Swahili (the Swahili coast was a particularly influential hub of commerce, maintaining contact with Bantus, Arabs and (eventually) Europeans).
Their Southeast Asian influences give them a distinct identity among possible new civs.)
The Malagasy (They would be a great civilization to represent southern Africa besides the Bantu, having played an important role in the Indian Ocean trade and forging a significant empire in the 16th century.
The Kanem (representing the Sahelian kingdoms around modern day Chad and Niger, where as the Ethiopians have an emphasis fighting from a distance and Malians are an economic jack of all trades, the Kanem would be more a military powerhouse).