With Stardock's help, it's fixed. The problem was image file names over 50 char. long! Oddly I'd used the same naming conventions that SD uses in their default LUNA skin

- I'm surprized it hasn't happened to other skinners. I had just changed the word "blue" to "envision" in the image file name, which put me over the limit. Stardock is now aware of the bug and are taking steps to eliminate it.
Sorry for all the problems, but the solution was one I'd have never expected.