(I loved those talks of tiny demons, probably one of my fave things!)
Tiny monsters are totally a thing, at least as far as I’m concerned. If any of the little guys like Sam die and hold a grudge, they’ll have the same ability to stick around and haunt. Vampires are great too – since in the Supernatural world, all they need is to drink the blood of a vampire, it isn’t even hard to become one! But then they need to deal with finding blood, and tinies like them are few and far between. They might have to risk a human or two, sneaking around while they’re asleep. The bite marks might be mistaken for mosquito bites in the morning.
The poor wendigos would have all the sad stories, lost and alone and forced to turn to cannibalism (or, eagerly turning to cannibalism, depending on their personality).
We might have a few plans for tiny monsters that we’ve bandied about a few times 😉