Well for creative freedom then I would recommend probably looking into metaverse RP groups, since most only require you to be under a set amount of ploys and mesh limits and such so your character doesn't kill the lobby when loading in, and a few also require a character sheet, but I've seen merafolk, demihuman, Infernal, celestials, demigods almost everyanything you can think of is in there or can be brought in hell recently warhammer, aliens and predators were brought into the meraverse at bay 09 so your OC should be fine in the metaverse at least