I haven't played P4M a lot so I don't know. Although I believe the thumbnail should represent the level, in the sense that amongst hundreds of levels in the game you choose a lvl to play according to what you see on the thumbnail, that was not really my point.
You are amazing Sherlock. First you raise the issue about the thumbnail being inconsistent with the level (the greys are not there) and then you challenge it by saying why the thumbnail has to fit in the game....hehe. Dr.Jeckil and Mr. Hide would fit better than Sherlock... I am only kidding tho.