Tieflings and warlocks have a great Ravenloft vibe IMO. Savage dragonborn warriors with Slavic or Romanian overtones could be neat as well. And nothing beats cruel-hearted, unseelie eladrin lords.
Well, the Ravenloft that I most accurately remember (and it could be horribly distorted) was xenophobic to the point of hysteria, much like the stereotypical "Wallachias" of the Dracula-style movies. Insular, frightened, and over-protective, these villages shut their doors and their minds to all that is outside because everything outside -- from the wind to the sun to the ever-present mist -- is alien, evil, and possessed of a black soul of corruption.
A man walkin' around with devil horns or a dragon's maw or who can step in and out of space is going to be mobbed and killed by the first yokel strike team the village can assemble in a setting like that.
Now, it's possible that this isn't entirely accurate to the rest of the way the world has seen it, and instead has mostly been from my own DM's particular style. But those things you mention, in the Ravenloft I'm aware of, would all be monsters. Not PC's. It would be like making PC's who are "half-vampire" or somesuch -- an affront to the roots of gothic horror that treats the Other as something always to be terrified of.
Now maybe those would all work in a horror setting where PC's got to play as monsters (I'm looking forward to a werewolf PC!), but Ravenloft wasn't really that setting, AFAIR. But, again, that could've just been my DM's take on it.