Nookie (thanks once again) has written a guide, how to theme KBFX, which I've reviewed and am glad to announce. You can find it in the how to section, by pressing on the button there or by clicking the following link:

KBFX create your own themes

In this guide you can learn what images you have to create and what size and name they should have.
If you follow the instructions, you should be able to create a theme within one hour (also depending on your computer art skills, of course).

Have a lot of fun, making a kbfx look of your own. We're very glad to meet the results on kde-look.org.

Nathanael Gogniat