If you happened to play Berzerk while it was still in the prototype/testing phase - instead of the stenciled robot/logo sideart, this is most likely the side art you saw.
Under blacklights, I bet this looked pretty cool. But it actually kinda reminds me of the US box art for Mega Man, under normal lighting... I'm glad they stuck with the production artwork. And according to McNeil, the bezel artwork never changed... It was the same as the production art.
http://www.rotheblog.com/2010/10/cla...e-alan-mcneil/