A nifty feature that was added a couple of months ago to Google Image Search lets your restrict the image search results to a site and when clicked "similar" next to one of the images, Google will only show similar images from the site in question. For example, if you search for [paris site:wikipedia.org] and click "similar" next to a photo of the Eiffel Tour, Google will now show pictures of the Eiffel Tour and other similar monuments from Paris, but only if they're on Wikipedia. The results includes: images, maps, flags, logos etc.
Also, note that Image Search's site: operator no longer takes into account the URL of the image -- meaning, if a blog includes an image from Flickr, you'll still be able to find the image when you restrict the image results to the blog's domain or subdomain. "In the past, the [site:] operator filtered based on the image URL, not based on the URL of web pages linking to the images. Now, the operator will run your search over web sites that include images, no matter where the images are hosted, which removes a lot of noise from your results and gives you more control over what you're searching for."