Go ahead!
Note, though: I was trying to play one of Salmoneous' levels with him, and it wouldn't work, apparently because we had different versions. I'm not sure what constitutes a version; any change may well make the level incompatible with the original. If it works though, great
I'll probably be updating the graphics/adding custom music sometime soon, where 'soon' is understood to mean 'a point of time in the future'.