In the previous post I said: "I have no idea what they meant to the story", and I think that's an interesting point that you can see expressed in many professionally done book covers. The cover doesn't actually have to have much to do with the story. Of course it's nice when it does, even if only tangentially or incidentally, but that's not really what the cover is for. The cover is to get you to pick up the book in the first place. Once you've read the book and decided that you loved or hated it, the cover has become something of an irrelevance (except in those extremely rare cases where the cover hits a perfect note that you want to look at often).
You can see this expressed on many of those covers: sod the story, no one's going to care about the story if they don't pick up the book first, first and foremost get their attention. If the reader is going to spent all their time trying to match up the blonde with the big candles on the front with a character in the story then you've probably lost the reader anyway.