Considering that Indians, along with construction workers and knights, where of the first themes, it might be nice to bring back a new batch of them, in a completely new way.
Instead of being pitted against cowboys, they are pitted against different Indian tribes, allowing children to become more aware of native americans and learn that not all Indians lived in tipi's.
At least two, perhaps more tribes could be included in this. It would require some good research to find tribes that could be portrayed with playmobil and are very different from each other due to hairstyles, build style, warpaint, etc.
Some weaponry and objects of the stone age theme could be used again I am sure.
At least this gives them the chance to make an original indian village set instead of doing the same thing yet again.. The tipi could still be featured in a smaller set, but the village could be wooden huts.
Aside from the usual sets: Indian village, individual indian house with family, hunting party with bisons, shaman, they could also make a waterfall set with a hidden cave behind the waterfall where clickies can hide.