Apparel. Obvious stuff like clothing. Things like key chains, pins... If it's a band, how about guitar picks with the bands name and/or logo on it? Drum sticks with logo/name as well. How big is the band? How many people listen to them? Depending on the answer, you could buy some of the same guitars that the guitarist(s?) use and get them painted or done up to look like the guitar(s) the band uses. Limited edition run of 5 or somethin
Sell CD packages that come with small picture books/making of/signed pictures/whatever.
I dunno, that's what I'd do.