As artists’ biographies go, those of Wallace Berman and Richard Prince could hardly be more different. Berman, who died at 50 in 1976, the victim of a drunken driver, was a kind of Beat guru flying just below the radar, showing his work in only one conventional gallery exhibition during his lifetime and popping into rare view in strange places: a cameo in “Easy Rider”; the cover of “Sgt. Pepper’s Lonely Hearts Club Band,” where his face is wedged next to Tony Curtis’s, just below Jung’s.