First--the side art. If the invaders bring back good memories for you, stick to it. Sure people will have an opinion of your cab on here, but you're the one who will be looking at it and playing it in your home every day. If you're REALLY worried about what other people have already done, definitely don't do black with blue t-molding

You could always use the graphics from "Space Armada" (the INTV Space Invaders knock-off).
I'm pretty sure the invaders shown in the picture of the "other guy's" cab are actually these:
http://www.whatisblik.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=B&Product_Code=BL-106APowered USB hubs are grand.
Part of my problem was that I spent WAY too much time planning. In the end I had a ton of ideas, but most weren't practical in the end. I figured I could fit two six-button layouts and a 2-1/4" trackball on a 24" Frogger control panel. It looked good on the computer, but once I made a mock-up everything seemed crowded. Here's some brief opinions on your list:
lucite or plexiglass - Plexi is cheaper and for what you're using it for it won't matter.
amount of angle on the action buttons - Do you mean the angle of the control panel surface (usually 10? or so) or the angle of the buttons on it? (mock it up and see what's comfortable.)
type of casters to use - I wouldn't use casters again.
micro switch or leaf buttons - I like leafs mainly for the noise factor. It's harder to find shiny, new ones though.
where to add shift and other buttons - as out-of-the-way as possible. I actually don't have shift buttons
where to add power button - On top of the cab
Where to get the fluorescent light - "under-counter" fluorescent fixtures are $8 with bulb @ Walmart
adding power within the cab - do you mean like a power strip?
dust washer above or below - I prefer below, but I butchered my overlay so they're on top.
CP surface mount or underneath - T-nuts look nicer. Mine bolts are above since I have a metal CP
mamewah or a different front end - I like Mamewah, but others like Mala and Atomic have really improved in the last year. Most all now offer ways to customize the graphics.
Pretty much all others are straight personal opinion.
Sorry this got so long.