Bit flashback for Cami's quotes:
Is not fuzzy's idea, the BG doesn't have to change like from desert to jungle, the idea is that the place where your sticks are has to morph in some way, if you read the examples I gave on the frontpage, you'll get the idea.
Other reference:
Shaffy, the idea of having a changing background is that your sticks gotta interact with it or be affected by it's change/movement, so if you're going to do something like hogwarts' stairs, it might be a little bit boring to watch if your sticks will continue in the same "direction".
She also said if "your sticks must fight in
an environment...", still from the front page.
So judging from my understanding, I think we just use only one background theme (means not changing it into completely different background) that is not static - it has to be dynamic in other word - AND affect the sticks in some way, relating to the BG change.
Hope I'm getting this right.