This Flickr gallery has even more examples. Windows product design team members Denise Trabona and Samuel Moreau explain in the post that it wasn't just about finding good-looking images, but also about figuring out "how the image flowed under the new task bar and striking the right balance between visually compelling, and not too distracting when it came to finding that important file on your desktop."
Not sure if they fully achieved that "not too distracting" part, but these are a few of our favorites.
Credit: Will Austin
Credit: Paul Hwang and Benjamin Lee of Nanosphere
Credit: Punga
Credit: Osmand Nosse