here's another idea, for the next project... band symbols.... obviously not the logos directly, but there are a lot of groups that have a huge following, that have identifiable symbols that are related to the band, either the band, or from an album... the possibilities are literally endless. i haven't seen anything like this yet either, and i'm sure they would go like hotcakes.
pink floyd - prism, moon, wall, cow, pig, .....too many here to list..... (you could do a whole collection with these)
zeppelin - I (feather), II (celtic), III (rings), IV (zoso), zeppelin (blimp)
stones/rocky horror - lips
kiss - tongue, cat whiskers
elton john - yellow brick road, over the top glasses
AC/DC - bolt (red on black, not "flash" yellow on red), TNT, big ...um... Sphere's ? (lol)
Ozzy - gory bat/dove/rat
Emerson Lake Palmer - big HR geiger references
Grateful Dead - LOTS here too
Bowe, Deadmau5, black flag, yes, green day, red hot chili peppers, beetles, etc, etc, etc......
... you could go on for days.....