Well what comes to mind first for a general theme is to just play off of the title.
I'd say going with gears and mechanical looking images would work pretty well, as long as its consistently used throughout the entire cabinet. That would entail losing the reference to Indy. Somebody might pick up on the title and say its from an Indy movie, but if its the phrase that you like the most, there is no need for Indy to be there at all.
I personally would go with a more rustic, broken down look for the gears. All old and weathered and such. I'm sure you could dig up a fair amount of stuff just through doing some Google Image searches. If anything you could find what you like, tweak the colors in whatever program you use, and make it look more aged.
But the most important thing is to just make many, many alternative marquees. Just play around until you find something that just "fits" and you love.