It would be awesome if we could get more tribal building pieces and decorations like Darfari, Tribal Himelian or Kushites. We could even get new T1 and T2 building pieces as well as new warpaint.
Kush was actually a pretty advanced kingdom with actual cities.
Darfari architecture and decorations are already pretty well represented in the game, although not all of them can be built or placed by players. Tribal Himelian buildings would probably look pretty similar in style to the Cimmerians at the Mounds of the Dead. Even the Cimmerian fur armor is thematically suitable, except for the hats.