This seem to be all over the place now, but as far as I can see, the image linked to is very often the wallpaper at Virgin Digital – and this lacks some vital hints at the left, where the image is cut off. So, I cloned it back in.
Have a look at the high resloution picture, and see if you can find all 72 bands. (Hey, maybe it’s possible to find some that the artist(s) didn’t think of, too? ;))