Over on Flickr, one of the guys from the JJ found these photos of some very cool motorcycle engines that a fellow named Gordon Calder has photoshopped out of other photos, and put them on a black background for maximum detail and effect.
The engines range from a Slabside Shovel, to an Indian Chief, Villocette, and Crocker. There are two pages (with 26 engines in all) over there. Once you click on the thumbnail, you are able to bring them up in four sizes (look for the tab that says "all sizes" in the upper L/H), two sizes being perfect for wallpaper. Do yourself a favor, and go check them out: