You can find a TON of different metal band minis that would fit in this setting.
An orc band exists and is available from Impact Miniatures, I know Megaminis produces some aliens with instruments (including what looks like Cthulhu/zoidburg screaming into a mic) and a bunch of others.
Good luck on this, I'd be overjoyed to see this kind of setting done in mini form.
Especially if you keep Jack Black in it.