Hi

It is indeed the case that CEGUI is badly in need of some new and interesting skins.
I think what you have in the image you posted is really good; there is nothing that stands out and makes me think "ugh, I don't like that!"

One thing I would say - as general advice for any skin - is where possible, for the final 'source' imagery we use, if that were to be greyscale, it makes it easier to apply customised colours within CEGUI later - so as a final step in the process, desaturating the imagery, and maybe even ensuring the range of greys for each sub-part goes from 0 to 100% in value would maximise the possibilities. Whether you have to worry about that I think depends on whether you intend supplying the original vector based imagery, or something rendered to a raster image.
Don't worry too much about not being comfortable with XML / programming. Given some decent imagery to work with, I would be more than happy to handle that side of things.
Keep up posted on your progress and let us know if you have any other questions

CE.