It would be interesting if appearance was automatically decided by your Beliefs, with the hairstyle based on Barbarism/Civilization slider. For those unfamiliar with previous worlds, these hairs already exist ingame, so it shouldn't take much effort to add this.
Barbarism -5 to -3

Neutral -2 to 2

Civilization 3 to 5

(Nature/Industry would control facial hair. A full beard for Nature and a groomed moustache for Industry.)