Not a fan of the crazy style mismatch. The issue is that they're normally drawn in a game where the protagonist is a pixelated sprite. The sprite quality between the protagonist and the backgrounds is also a mess.
P.S. The Undertale title screen font is probably not the best to use, especially since it's awful with dialogue boxes.
EDIT: The game's been updated since, and a majority of my grievances have been alleviated.