The dominant cultures are the technomagical prophets, the mystic nomads, the martial ideologues, and the tribal hordes. Races and classes listed are merely the most common—all races have been known to inhabit all cultures—so you may choose whatever combination you feel best fits your character.
Other cultures: Other cultures are possible; feel free to discuss with us. Other races are also fine—we are generally allowing anything listed in the 4E PHB or PHB2 (adapted to PF as appropriate). The only exception is humans: there are none. It is possible to play a human, but there will be some restrictions—please discuss with us if interested.