okay, what I was explaining in my PM:
essentially you'd have an aesthetic based upon change of theme. Now, this would require the levels to be randomized, which can be achieved with level "segments." So the levels would randomly gen for a bit until your character runs into a tunnel at a certain length. he would then emerge in an alternate (randomized) world. for instance, the first level could always be the one you have. then you might emerge into a city scene where the music becomes 3/4 "swingy" time and the mood changes from bright and organic to sleek and "nightlife"-ish.
you could have an industrial factory, an underwater area, etc.