I have some experience with modding... if you know where to find images use as icons, as the leader of the Chachapoya and etc., we could work together to bring such a mod into fruition.
Ok well I can do that quick here are some images:
Possible Buildings/Improvements:
http://www.fertur-travel.com/blog/wp-content/uploads/2009/08/revash3-300x225.jpg
A picture of a Chullpa: (A Cliffside Mausoleum). Very important and distinct, mumification appears at its earliest in the Andes in these Mausoleums. They tended to be built on the edges of cliffaces/rugged terrain and are extremely hard to reach.
The Chachapoyan burial places are quite exquisite.
Here is a picture of Chachapoyan Sarcophagi which show both their Amazonian and Andean roots:
http://xenohistorian.faithweb.com/latinam/chachapoya1.jpg
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The Chachapoya were also famous for their forts/city construction. Their forts allowed them to fight against both northern invaders and the Inca for centuries. Their round forts can be seen easily via a google search, but here are some links/pics too.
http://cache.virtualtourist.com/3468476-Kuelap-Chachapoyas.jpg
http://images.travelpod.com/users/k...tist-rendering-of-what-kuelap-looked-like.jpg
Now Chachapoyan unique units will/would be harder to implement. They however were famous for their maces and slingers. (Their slingers were more feared than Incan Slingers ever were) The problem is slingers are already in game.
That leaves us forced to use something with their maces.
I can't give you any great pictures for a Chachapoyan Mace Warrior (Or give you a better name really) but here are some pictures from a couple of documentaries:
http://www.natgeoprogramming.com/images/categoryimages/file/inflightimp-1909.jpg
http://tabulorasa.info/uploads/posts/2011-02/1298189748_e64a1601-7cd2-458a-ab99-082672503ec8.jpg
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And here is a picture that could be used for the Chachapoyan Standard/flag/Symbol:
http://upload.wikimedia.org/wikipedia/en/5/5d/Abisco_or_Pajaten.jpg
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Some pictures that could help I hope if you did want to make a mod of them in the future.
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Some possible cities could include but are not limited to:
Kuelap, Revash, Huancas, Purun Llacta, Yalape, Olan, Leymebamba, Chilchos, Gran Vilaya, Condors Lagoon, Congona, Jalca Grande, Macro, Yamon, Rentama, Iyacyecuj, Meseta, Chachapoyas, and not all cities are listed here (While I know some about their culture, I am still by no means an expert).
The leader would be limited to one of their latter leaders before their end at the hands of both Incan revenge/Smallpox/Spanish conquest; Blas Valera.