Here's the first design I've added to my shop over on Zazzle. You can add it to other items by clicking on the shirt shown, then on "see all..." in the "Choose your style and color".
Also, click on this image and it will take you to flickr. Click on "all sizes" there, and you can find a size appropriate for your desktop or mobile wallpaper needs.
UPDATE! Zazzle has free shipping right now, if you use code HOLIDAYSHIPS . I don't know how long this will last.