Speaking of the Steam screenshots feature, take a picture, don't upload it, instead, click on the view on disk button, then open up the image and the thumbnail in your favorite image editor, then save it as a .jpg and overwrite them, then go back to your screenshots by clicking View and clicking Screenshots, THEN upload your screenshot
The result of me doing so is this (screenshot taken on Monday, August 15, 2011)
http://steamcommunity.com/id/Masterlegodude/screenshots/