Google Images provide some unique search features that aren’t available in other photo sharing sites like Flickr, Zooomr, Photobucket, Facebook, Corbis, etc.
For instance, with Google Images you can limit search to just pictures that have a face and are colored. Or you could ask Google to only show wallpaper sized pictures and that too of JPEG type. There’s also an option to filter out adult images from the result set.
Taking a cue from Google Images, I have put this Image Search page that brings all the Google goodies to other photo sharing and blogging websites as well.
Type in a search term and select a site that you want to search from the drop down menu. You may refine images results by face, image extension, size, picture color, adult rating, etc.
Internally, it uses Google AJAX API and the site: operator but some may find it slightly more convenient than using the advanced search page of Google Images.
Give it a try specially the "US Govt." option that finds official pictures uploaded on .gov sites.