Some forums have the option to play a song on user profiles and I think that'd be sweet.
An example would be, again, FeralFront (I'm always saying they have good ideas)...so, James? >: )
It's an interesting idea. I'm not sure how viable it is, though, given SMF and the mods that available. There's also possible trouble with copyrights, and people being irritated by autoplay if they go on someone's profile. ;) That's not to say that it can't be done, but it might take some looking into and there are some problems that would likely have to be smoothed out.
I'm not sure, but it might be more readily possible to allow people to put YouTube videos on their profile. Perhaps that would be a viable compromise, if somewhat diluting the effect.
If we look into introducing something like this, I'm sorry to say that it will probably be on the backburner for a while -- there's a bunch of other stuff under the hood that I really ought to get around to fixing or changing, that I haven't yet.
I should specify that the music only plays when clicked on, but otherwise, that sounds good.