There can be OCs as well.

Romance should be secondary to the main plot (which we need to come up with) M/M, M/F and F/F is okay. Action, gore, violence, blood, and so on is allowed. The vampires are the BAD guys. No vampire romance. Spike (Possibly Angel) are the only exception since they have souls. There should be a lot of creativity on the kind of demons and such that the gang fights. 

It does not have to be 100% accurate to the TV show.