The Conquests scenerios have two or three eras in their tech tree, but the cities and leaders don't change in appearence, its just to signifify that each period in history had more than one era.
By this I mean, is the first basic techs on the first "Era" of the tree, and then the more advanced ones(Like the Incans, Pueblos, Azteks had) on a second Page.
I suggest these names for the three eras in the tech tree
Nomadic Era(Basically the Stone Age, that the N.American and Tupi tribe were in when the colonists from the Old World arrived)
Kingdom Era(The Bronze Age, basically what the Incans, Azteks and more advanced N.Americans were when the conquisdors from the Old World nation of Spain arrived during the 15th and 16th centuries). There was also N.American tribe that had begun to build pyramids like the Azteks, but they dissapeared before the 15th century, I forgot there name however, maybe Mobilize knows.
Post-Columbian Era: This is after the Colonists arrived, but the purposes of this mod, before the Colonists arrived in drooves, destroying the Azteks and Incans, putting the N.Americans threw an expierence much like the Nazi Germany's Concentration Camps etc. This is where Contact-Europe is researched, which nets all tribes horses(The Iroquios Unique Unit, and the other N.American cavalry), and guns(the Native Shooter Unit, for NA tribes) also the Incans would get Cavalry early I'd imagine, although its not historical, the Incans would get Llama riders in the 2nd era.
Lets see.
Governments:
Anarchy
Despotism(Usually the Starting Government In Civ3)
Blood Cult(like that practiced by the Azteks and Mayans)
Tribal Council(Possible alternive to despotism as a starting government. The N.American tribes practiced this form of Government, an early tech in era-one)
Monarchy(Like that practiced by the Incans, researched in 2nd age)
Tech names:
Era One:
(Check out R8XFT's sample tech tree)
Missing Techs:
1. Tribal Council
2. Shamanism(first religious tech)
Era Two:
1. Bronze Working
2. Monarchy
3. Road Building
4. Polytheisism(The Incans, Azteks, Mayans believed in many gods)
5. Arctecture(For Temples, the Pyramids, or Chichen Ista etc)
6. Ball Games
7. Code of Laws
8. Ship Building(Native boat building advances beyond canoes and rafts)
Era Three:
1. Contact-Europe(For Horses and Guns)
2. Catholism/Christianity(last religious tech)
PS: Thanks again R8XFT, I'll probably add the Caribs in myself actually Unexisted(using the Masked Leaderhead of coarse), since there is a way to add civs, as long as the number doesn't go past 31. But that download link isn't working! And neither is the one for Athaluapa. Darnit!
. I'll upload the full files when I upload the mod...but for now, here are some previews:
) and gave it features from other leaderheads. I found a headdress online and painted that in, along with a forest scene for the backdrop (although you can barely see that). Here's the all-important previews:
. As per the previous two leaderheads, there's basic 3D animation, which is smooth once again, but only basic expressions change. Now that these three leaderheads are done, it gives us 14-15 tribes for the mod. That should definately be enough for now 
