Ray is correct about there being no plans to currently add any further native nations for release 2. However, the leaderheads AbsintheRed has found are quite promising.
The female leaderhead would not work for Cockacoeske. Her dress and background are more suited to tribes further west. Cockacoeske was Queen of the Pumunkey, a tribe within the Powhatan Confederacy in Virginia. She was the alternate leader we considered for the Algonquian. But the leaderhead could be used for other nations.
As for Jasaw, the leaderhead is very good, but personally I would like to use him for another Mesoamerican civ other than the Mayan which we already have. Maybe a civ a bit further south, as we already have the Aztec, Zapotec, Mixtec and Mayan in that area. Also Jasaw lived nearly 800 years before Columbus's arrival.
Purhepecha or more commonly known as the Tarascans, are also in the same area as the Mesoamerican civs above. They resided just to the north of the Aztecs. The leaderhead is good, and I think by changing the background and losing the checkered pattern of his clothes and replacing it with a more neutral color, he could be used to represent several native civs.
Nice work AbsintheRed in finding some good quality leaderheads.