I know some popular slashers that i mostly have seen in fanfics:
Brahms (The boy)
Ghostface (Scream, for some reason he has 3 ppl as them billy, stu from the movie and danny from the game DBD)
The sinclaris (House of wax, Vincent and bo are the most popular but maybe you can add Lester if you want)
These are just suggestions i don't want to force you into putting them into the game. This game has is an amazing idea and i hope you get to finish it