Thanks for the comments.
I'm completely torn on an underlay. My original plan was no overlay. Just go with the wood (which looks nice) and black (tmolding, coin door, CPs) look. But since I ended up going with a lighted button/coin door Blue v. Green theme, I've contemplated a sort of galaga-style graphic, continuing a blue v. green theme on the underlay.
I'll have to continue my contemplation, but the other factor is cost. I've been trying to keep this as inexpensive as possible and hoping to even come in under $500. That sounds crazy, I know, but I think I might actually pull it off. I haven't added up the numbers recently, but I'm pretty close. For a brand new cab with brand new hardware (minus the joysticks, monitor, pc and glass) I think $500 is a number to be proud of. But we'll see how it all shakes out in the wash

I really wish I could get a decent pic of the green buttons on the Player2 CP. The translucents look GREAT (which is a testament to whammoed & Knievl, since green translucent leafs are notoriously difficult to light), but unfortunately they photograph horribly. Even though (to my eye) the green color matches the green of the coin reject, it doesn't come off that way to my camera. You can see from the first post in this thread that the green doesn't quite look right in the pics.
When I next get some time (probably not til June) I'll try and tweak the colors using the coin-reject color as a reference since it photographs well. At the same time, I'll fill this thread out with some more info.