It's not necessarily "Good Vibrations"-related but I for one am planning on hanging a (as sizable as possible) framed print of the 1976
Rolling Stone cover (featuring Brian in bathrobe with surfboard) as soon as I have my
own own place (and not live in digs, as they say).
That being said you might find some decent stuff if you search for concert promo posters of Brian's (earlier) solo gigs. There were some real funky ones.