I've spent some time on and off over the last 4 years building an arcade cab, gathering up the files required, doing the homework to make it all work, and designing a layout. I figured now that I'm done with my layout I'd share it if anyone had some interest in using it. I know there are a lot of good layouts out there, and I certainly was inspired by *cough borrowed from cough* a few of them. I won't be able to credit the people I borrowed ideas from because I forget where I saw them or who made them.
The most interesting part, to me, was the journey from how I envisioned my front-end to look in my head vs how it actually turned out in the end. You learn a lot of things along the way, like it's a good idea to keep the window you display your boxes/marquees in fairly small because there is a large amount of box shots, marquees, flyers, etc that are only available in a really low resolution. If the window is too big, when the box or other misc artwork is displayed, it looks like crap. Also, having a layout where all the windows are generally in the same position for each platform is a great idea, otherwise it's confusing when you jump from system to system.
Some of the things I tried to do with this layout set were:
1) keep high quality source files on all the art used to create them, so they can be scaled properly to fit where needed without looking terrible. This was kind of the whole point of this set. I hate to pat myself on the back, but I'm not an artist, and when you look at this set in it's native resolution it's really clean and beautiful. There are no crappy cutouts where someone hastily chopped off mario's foot or something. I painstakingly cut out each and every piece of art from high resolution source files in order to make this set look as high quality as possible. Mine are in 640x480 so that it works great on arcade cabinets running CRT monitors. However, I have all the source photoshop files available so you can tweak them however you want, add infoboxes, move stuff around, or use the templates to create your own layouts for the systems you might want that I didn't. With just a little re-work you could even remake them in higher resolutions.
2) use mascots/artwork that are unique to each platform whenever possible... for example I didn't use Altered Beast in my Sega Genesis layout because it was originally an arcade game... I used other games on the Genesis that were amazing and original like Phantasy Star, and Sonic. Another example would be using period appropriate art for a platform, like using art from the original Zelda for the NES layout and not being tempted to use art from a different era Link such as the super nintendo. I had to make a couple of exceptions for platforms that didn't have enough unique mascots to fill the space, but overall I was able to stay consistent. I feel like doing these kinds of things really help make each layout look appropriate for the platform it represents.
3) find and/or create the best possible beauty shots of the platform as the centerpiece for each layout. That took a lot of work. It's hard to find good, high quality pictures of consoles on the web! I was very careful when cutting them out, colorizing them, and just basically tweaking them to look fantastic in photoshop. I was tired of finding thumbnails of other peoples layouts and thinking "Oooh! That looks cool!" only to download it and see all the problems with it in it's native resolution.
4) maintain a colorscheme/backdrop theme that is related to the platform. For instance, using a black grid with grey stripes for the Genesis (that's what was on the genesis box and most of the game boxes) and a white grid with grey stripes for the sega master system (ditto). Blue to black gradient for NES. Black backdrop with grey 4 button controller art from SNES boxes. Etc.

Anyway, if I see some replies here showing interest I'll take the time to organize it all and upload it. I would just have to find a place to host it all, as the .psd files are kinda large. You can see a sample of them all in the picture above (the top row contains samples of what some of the layouts look like with artwork and game lists, the bottom 3 rows I left empty in this picture).