Eweweweh… yuck.
Others with more experience might have better suggestions...

But someone thought it would be a good idea to spray paint an old pacman cabinet … probably to disguise it for another game:
https://forums.arcade-museum.com/showpost.php?p=646667&postcount=16
Anyway; Believe it or not I had marginal success removing the spray paint with

xylene.

I'd defiantly test is sparingly before committing... and I'd wait for others to chime in on less solventy type solutions. I have no idea what this stuff would do to BG paint. Like said; use the solvent on a rag and work sparingly on the BG... dont' apply directly to the air as you risk getting the solvent between the glass and the art where it'll definably soften and/or break the surface tension between the glass and art - leading to flaking down the road.