Interesting @MastaZavr but maybe the walls could go with a different treatment? Like maybe since the back wall sometimes has shelves showing some depth, why not make a facing wall tile to all of the walls have a little depth?
Here's a shot of the level selection screen. The selected level is blurred in the background, and it seamlessly fades into the level (and hides the loading :-P). This also shows that the level titles get more 'corrupted' as the game goes on. Fun fact: the level titles will all line up to make a poem, but each relates to the theme of each level, too.