I am quite found of any tool that allow to search inside the contents of images on the web. One such tool is Multicolr Search Lab Flickr set. I really like it because it is able to look for images based on their colors. But not only that. Today they include a lot more images since they collected 10 millions Creative Commons images from Flickr.com.
Multicolr Search Labs
It was an impressive tool, it’s now a useful tool.