I'm currently wrangling with one of my publishing houses about cover art. I'm sure someone else might love the covers I've been presented, and it's clear the artist is super skilled, but she/he is not quite getting it. The cover has to fit the tone of the book. Granted, not everything will be the same as described in the story, but it has to follow genre/tone and be eye-catching.
Some of my favorite covers I've gotten through the years, to list a few: