Free photo of a pair of white socks. One sock is noticeably cleaner than the other. Believe it or not, the clean sock was washed by hand and the dirtier one went through the laundry machine. This picture is free for any use.
This work is dedicated to the Public Domain. For non-US use it is also placed under a Creative Commons CC0 designation. If you do use the photo, please consider giving credit and linking back to the site. This isn't required, but it's a very good way to support our efforts. Just something like, "Photo courtesy photos-public-domain.com".