Your story sounds interesting, but I've never seen horror pulled off too well in VX. As soon as a cartoon monster appears on screen all the credibility disappears. Perhaps it would be more 'scary' if the player didn't get to see the demons, and saw just a shadow or something instead? Not very original, but just a suggestion.
As for getting sprites done, there are a few people on forums that take requests, but I always suggest giving it a go yourself. Just load a few other sprites and splice together bits that you like, recolour some parts (pixel by pixel, follow all the shading - don't be lazy) and you're done. I used to do this quite a bit and it would take me 5 minutes to recolour/edit a sprite; it's worth learning how to do it all. If it looks awful, run back crying