[@Weird Tales] In a sense. You have to use character concepts from any DC media whether it is videogames, tv shows, movies, comics, or books. You can also use characters from Elseworlds Stories or One-Shots and even other DC-Affiliated imprints like Vertigo and Wildstorm as long as they fit the overall atmosphere. The characters you create must draw on those characters but you can re-imagine them in any way you think is interesting. Like Zsasz being a mob hitman in Gotham or Copperhead being a female south-american assassin in Arkham Origins. As long as your PC has some kind of tie to or is inspired by an existing DC character, anything goes. 

This is a DC rp so I think it'd be better to have re-imagined DC characters than completely new OCs. And it still gives you tons of creative freedom. 

[@Zoldyck], thank you and Weird Tales for your interest. If I get at least four people interested I'll make an OOC, but it is never too late to apply. Neveeeeerrrrr.