A few for starters:
I like the original Pac-Man graphics
I have a soft spot for the original Dragons Lair, but don't know why that would make sense on the Picade since I don't have that running :-)
Obviously the original Star Wars cabinet has to be on my list, but again this doesn't feel like a good fit given how well it works with a stick :-)
I think there would be a nice little side line for full cabinet graphics, side panel laminates, marquee, screen border and control panel.
Suggestions rather then requests, otherwise you will be working all hours :-)