Google announced that “Similar Images” features is graduated from Google Labs and is now a permanent feature in Google Images. You can try it out by clicking on "Find similar images" below the most popular images in search results. For e.g., if you search for [Ancient Egypt], Google Images’ll provide you with a rich variety of results, including pyramids, maps, relics, drawings and other types of images. Instead of poring through hundreds of images, now you can use "Find similar images" link to find more pictures.