I created these for my own desktop. Should anybody else be interested please feel free to download and use (subject to licence terms below).
Edit: Added a third.
All pictures taken with a Nikon D50 and post-processed to adjust the colour curve in The GIMP. The third has had a slight vignette added.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.