Affiliates give extra PT for images and literature that they're included in.
Affiliates are species that are pre-approved to be allowed to interact in Gaia's World. OCs are other species or other characters, that have not been vetted, and may not be allowed to be in event or lore submissions. However, OCs will always be allowed in simple quests or general art, but their presence will be considered non-canon. Now, if your OC is a 'generic species,' such as a centaur, unicorn, elf, demon, or other basic fantasy species, those are allowed in all activities and could be included in lore, since they could feasibly exist in Gaia's World already. That said, an OC of a generic species wouldn't be counted for the Affiliate bonus.
While you get a bonus to PT for adding your OCs to pieces, you get a greater bonus for using Affiliate species, and you also get a greater bonus from including a creature from another ARPG. The bonus is increased further if the character is of a species from an Affiliated ARPG.
These species are affiliated with the group and will receive bonuses in art that include them. We encourage you check them out, not only for the bonus but because they're all neat species you might enjoy!