[Cairenn]

Currently the only thing possible is skinning (graphics replacement) of the existing windows. As you can see, I've moved your post to the Developers Discussion section of the forums. This is the area that has the information on what is possible and how to do it. Check out the Tutorials section, in particular, for precise info on what is currently possible. More generalized info and discussion is throughout the rest of the Dev Discussions section. Extremely in-depth discussions on one specific thing (example, how to work with graphics and graphics editors) would be in the appropriate forum.