Sorry, forgot to reply neph, working late schedule this week. Anyways, I'll churn out my character this weekend. And to finally answer your question, no, don't really have any ideas. Never was able to get into Supernatural or the other things you reference. However, I did enjoy a show called reaper that had escaped souls, which you could consider? Some characters might not want to be angels or demons, but could be escaped souls (possibly even from heaven) so they'd be more of a middle ground from the demon/angel to human spectrum, without having as much powers.
Elaborating on the escaped soul idea from Reaper, if they were an arson in life, they would have fire powers. A serial killer who used chainsaws could turn his hand into a chainsaw. Kinda goofy, might be out of your setting, but worth considering I suppose.