The Mappy style cab would be a good candidate for a "showcase" monitor in place of the giant marquee. Stick an LCD in there and everyone in the room can see whats goin' on.
I've always wanted to figure out a way to get a marquee shaped LCD (maybe from a slot machine?) and put it in the Marqee spot. Then have the front end or CP wizard show the marquee of game you're playing as you play it. Maybe slide show through some of the artwork as well. And then, as mentioned, the game play so the ladies would having something to see.

I always thought Narc had an interesting layout. In fact I remember a version with a second monitor above it. I don't know if Williams made it or if the bowling alley where I saw it modded their machine. There was definitely a two tier Narc in my neighborhood growing up. Never any ladies watching though..... hmmm?
I agree with everyone else though, side art can be just as big a wow factor.