fantasy here!

If you really want to make a guro RP and make it great forget about types of victims etc and focus on the atmosphere created by the madness of the killer for example Tsutomu Miazaki believed himself to be a creature known as the Ratman due to his deformed hands and lived inside his own world governed by his grandfather. That's right his motivations had little to do with his media given nickname apart from the fact that he took pics of his victioms and used his drawing skills probably to make them live longer inside his mangas:) If you can get inside the killers head and simulate that then you can spice it up with violence, rape gore and so on Good luck!