I took a few pics from Relix of Phish on the Simpsons, you can find them below...
http://www2.bc.edu/~veino/pictures/phishsons.jpg <-- whole thing
http://www2.bc.edu/~veino/pictures/phishsonsfixed.jpg <--wallpaper, just the boys and Homer
http://www2.bc.edu/~veino/pictures/phishsonslights.jpg <--wallpaper, with lights that I added in photoshop
http://www2.bc.edu/~veino/pictures/Phishcrazy.gif <---wallpaper, animated gif, looks great with active desktop enabled, things go crazy ;-)
Can't wait for the episode, April 7th... Enjoy.