The ipdb.org page for Silverball Mania mentions that there is supposed to be a self portrait of the artist somewhere on the side of the silver ball reflection, but the writeup made it sound like they were talking about a different location.
"According to Kevin at the 2004 Texas Pinball Festival, some of the reflections in the silver balls on the sides are of Kevin himself" Source http://www.ipdb.org/machine.cgi?gid=2156
There's also supposed to be an image of his Jeep somewhere on one of the plastics.
G