The only bad art I've encountered in the world of publishing comes from either the author or the editor. Having said that, sometimes the sales team can completely destroy artwork. This stuff should often be left to designers. Authors, editors, and salesmen are good at their jobs. Leave the look to the designers . . . of course, marketing will never let that happen.

I'd love to see who is responsible for some of the excresence you can find in YA books, though . . .