So the story is kind of about a werewolf girl who escapes from a sanatorium/hospital for lycanthropes who have issues assimilating with humans. I have to flesh the plot out more, but I can't decide whether I want the story to be just about werewolves and humans or if I want to include other supernaturals (witches, faeries, ghosts, etc.) Particularly, this one character in my head just strikes me as a vampire. But as a reader who is sick of vampires, I am worried that by making him a vampire will piss off a lot of people. The story is not about vampires and the maybe vampire in question is not a love interest by any means. I thought it might be interesting to see how humans respond to different paranormal creatures based on what they are. For example, they may like witches whose powers can be beneficial but hate ghosts who haunt their homes. What do you think? Because vampires are overused, does that mean aspiring writers should leave them out of their works?
I don't think it matters if they're over used or not, what matters is how you write them. If they're the stereotypical type, then maybe reads will be annoyed that you put them in there, but if their different and add to the story then it shouldn't matter. After all, it is your story. Also, if you see that certain character as a vampire, then that is what he is; I don't think that it'll do any good trying to making him something else if you see him as a vampire.
Well, I'd say that vampires and werewolves both sort of fit into a "biological monster" model - you don't need magic and the supernatural for them. I'm not saying that they're easy to actually believe in, but that they're a _different_ suspension of disbelief, one that for me is less difficult than anything involving magic. So once you've got werewolves, for me vampires would come "free". Witches, fairies, ghosts, etc., would then have added cost, to continue the metaphor.
Leave any character out who does not have a specific role in the story. In other words, don't use a vampire if a human or another werewolf will do as well. I don't know your story. You know your story. Only you know exactly what is necessary to your story and what is gingerbread (i.e. gratuitous decoration).
Huh. Your comment above seems to perfectly parallel a favorite (of mine) Henry Mitchell quote about garden design: "Do not permit anything in the garden to be more costly, in material, than is necessary. If wood poles wil serve, don't use brick columns. If brick will do, don't use stone. If stone will do, don't use marble." It's interesting to see exactly the same guideline (the same in my view, anyway) applying to two entirely different pursuits.