I see that the skins currently up for download are all 800x600 and 1024x768. The touchscreen I've ordered is native 1280x1024, so that's the resolution that would look best on it.
Can I make a skin 1280x1024?
Yes, you can make a skin for any resolution.
Well, I don't know if "I" can. I'm a total Photoshop dummy. :-[
But it's good to know that it's possible. One more project for my backlog!