On a similar note, I've looked into background editing ... editing the actual texture for the background wouldn't be too hard, after all it's just two bitmaps layered on top of one another, stored in a rather strange format ... but there wouldn't be much point. Why? Well, unless you can edit the 3d geometry of the level as well then all you can really do is add logos, posters, that sort of thing ... you get what I'm saying.
Anyway, does anybody want that sort of limited background editing?