The problem is that these images are still rather far from what the themes themselves will look like. For example, in the theme, text styling is limited to what the user's browser is capable of. Text images can be used instead of actual displayed text for such things as headings, but in a CMS like Tiki, it's best to use actual text rather than text images for just about everything, because of the content being dynamic and multi-language. This means the text in your images won't be rendered as shown but instead will be text produced by the user's operating system and browser.
Also, the layout in the images isn't clear, in terms of what in the images needs to go into which of Tiki's page divs, etc. A Photoshop (or other image program) file to base a theme on needs to be basically a pixel-perfect representation of the final page, like a screenshot. This can be sliced up and the parts used for HTML background images and so on.
Themes could be made that are "inspired by" your images, but a lot of interpretation (that is, extra thinking by the theme maker) would be needed to get from those images to the finished theme. This could be an interesting project, but personally I don't have the time right now to do that (Tiki 1.10 is coming out soon and there is a lot of work to do to upgrade existing themes and so on).
If you could get the images closer to what the finished theme will look like (and no need for text labels, just the actual image components themselves, with any needed descriptions not part of the image file), that would make doing the theme a lot easier. Maybe by that time in the future my schedule won't be so full, also.