Yeah that's the tricky part - and probably a reason why most other multi-emulator skins you see have one indicated per screen and no visible menu, like retroGUI, say.
Everyone is going to have a different set of emulators that they run - and even that will change over time too probably. The set in those screenshots is just what I plan on running. And the same obviously goes for the help instructions too.
What I'm planning to do is prepare the source photoshop file so empty buttons can be added, buttons can be removed, and text/images can be changed. The downside is that to customise for your own needs you need to edit that file. I will provide a flat file as a PNG as well [edit - below], with empty template buttons, so people with any cheap old software that allows selecting sections, copying and pasting, should be able to do one up with the correct emulators to suit them.
There may be a better way but I don't know it yet.
This whole skin (well two, now) was me setting up a custom theme for my own cab so I didn't mind it working differently to how others do. I work in web design, and this is very similar to designing for kiosks, where you can take advantage of everything you know about the end platform. I don't mind sharing the work, but it's still primary a custom job
Since you've been gushing praise at me though, squirrellydw, I'll set something up for you
[edit - have attached 2 x 1280x960 below, with clean blank buttons ripe for duplicating, moving, adding labels and whatever]