Yeah, maybe furthering the Mesoamerican theme a bit would be good, for instance give them feather headresses and stuff.
Also you could give them more of a sacrifice theme. The Mesoamerican peoples thought it was essential to sacrifice people in order to, basically, stop the world from ending. It seems evil to modern ears but you could get some kind of interesting game mechanic out of it.
Maybe sacrificing population would bring down the Armageddon counter, or perhaps it would grant special abilities to their priests. For instance in Cholula they thought they had to keep sacrificing people to keep a stone in their temple strong that kept a deluge of water back that would drown the city. During the seige by the Spanish/Tlaxcalans they broke the stone in question, but this being the real world nothing happened. You could do something similiar here. Instead it could be about sacrificing the priest unit in question, in return you get something fantastic, the higher level the priest the better.