The original symbol of the Aztecs was an eagle having a human heart in his bill. But due to Christianity all symbols which somehow pointed to human sacrifice were soon altered by the Aztecs, either of fear or because they too started to share the Christian ethics yet still lived their Amerindian culture. Thus they didn't want to tell or couldn't accept themselves traces of human sacrifice in their culture anymore. Their hero-Godking Quetzalcoatl was turned into a peaceloving, monotheistic butterfly-sacrificing king who didn't perform human sacrifices anymore. The same has been told about other hero-kings (Nezahualcoyotl), but for some reason we find these ideas only in post-conquest sources...
Anyhow, as I see that you still add the one or the other civ and the train's not completely gone. May I point out that you don't have a single Canadian Indian civ? I mean Ojibwa and Cree both occupied vast areas compared to tribes like Mohicans, who were rather abysmal. Another question: Why did you include the Seneca additional to the Iroquois? IIRC, the Seneca were part of the Iroquois league. Or you could have the Tlingit from the coast.
And from South America, there is definitely a need for a northern Andean civ, either the Chimú or the Chibcha. The Incans have to cover all the Andes in your mod. That's like if you had only the Iroquois East of the Mississippi in the US...
Apropos Mississippi, it's somehow not satisfying that the so important Adena/Hopewell/Mississippi culture is not represented in the mod. The closest ethnicity in there are the Shawnee. I don't dislike the Shawnee but that's a bit poor to represent that culture. Why not Mississippi. I mean there wasn't a tribe called "Powhatan" either. It's just the name of a ruler...
f you don't like the names above, why not the Natchez?
If it was for me, I'd make the following changes:
Seneca --> Ojibwa
Mohican --> Chimu
Shawnee --> Missisippi/Natchez
?Navaho (Dené) --> Tlingit?
I know, it's your mod and you want it your way, so feel free to just ignore me.