For more design freedom, you can just put one big div over the whole thing, layering your page on top of the default page like this guy did (and he wrote some good tutorials about the process), but you lose all the functionality - his friend's list is custom coded, he can't do blogs, etc. I'm a bit curious as to why MySpace doesn't have classes assigned to the various blocks they use, so that people could reposition and format them as they wanted . . .
I played around with overwriting my whole page, and custom coding things, but decided that was silly. If I have to hard-code my friend's list, and then one of them decides to change their display name, that change won't show up on my page, and I feel that would be stealing from their individuality. Yeah, I realize it's just a silly name on MySpace, but still, who am I to say that someone should be called "Greg" instead of "...the groove". Of course, there's also the part of me that was tempted to put a silly page about how either looking at my profile had caused your MySpace account to be deleted or something like the stupid virus bulletins that I've seen going around, or creating a totally fake friend list that included random people who hadn't been friended.
Anyway, I ended up restoring everything to what it was before I started, since I feel that color, background, font changes don't really add anything of value.
Oh, and it's painful to work on this as MySpace's servers are slow as dirt, so you spend more time waiting for your changes to be submitted than you do writing/designing . . .