Well you can mount them the same way mirrors are mounted, with those clips.
Otherwise make a HUGE shadow box and start filling it up with marquees

There are three main types of marquees too. Vinyl, plexi, and glass. The Thunder one on my cabinet is a vinyl one that I sandwiched inbetween plexi.
Most of the classics (pacman, frogger, etc...) are glass.
My double dragon II is plexi/lexan.
Then there's neogeo which are inserts.