I think as far as the females go, Au Ra probably have the most diversity as far as the types of ethnic looks they can pull off with different facial features and skin tone.

It would've been nice if all of the races/genders had faces as varied as they do (Even male Au Ra feel pretty indistinct in this regard largely because of their eye shapes being very similar between their faces, save for the extremely unpopular "sad" face) because some of the original race/gender combos really suffer from same face syndrome.