The half-Vistani roleplay guide describes bonuses for Vistani tribes, however these aren't in the game. It would be neat to see some of the tribal effects available for half-Vistani PCs!
The simplest thing would be to provide a small skill bonus based on tribe, for example:
Kamii: MS/Hide
Equaar: Animal Empathy
Vatraska: Heal
Naiat: Perform
Corvara: Open Lock
Canjar: Spellcraft
Zarovan: Concentration
This could be done via a feat which is available for half-vistani to select (similar to how other races get to select racial feats).