I've posted a tweak I'd like to see in a different thread.. But now I've seen this, I'll add it here.
It'd be pretty cool to see the album art of your current song in the multitasking bar. - Sometimes, I don't know the song I'm listening to from just the song title, or the intro of the piece of music I'm listening to.
I've just made a quick mock-up on photoshop touch:
Why not simply temporarily replace the "Music"-symbol with the cover art - would make sense to me