BikeSnobNYC has a lovely (NSFW!) image that he pastes over ads and pictures in his screenshots of newspaper articles and Craiglist posts to great comic effect.
I liked the effect so much that I wanted an easy way to do it on every page. I have made a bookmarklet to do so: drag the "Approve" link below to your bookmarks bar and click it on any page with images. If you then hover over an image for one second, it will load the naked recumbent image rider, in the same dimensions, cropped to avoid distortion. Tested in Firefox and Chrome.
(The one-second delay is to prevent you from changing images by accidentally moving your mouse over them.)
Approve ← Drag this to your bookmarks bar!
Some pages to try it on: The Guardian, CNN, or our beloved Wildcat Rock Machine's one blogular site.