When you search for an image in Google Image Search, (images.google.com) look for the drop-down selector on the upper blue stripe. The first choice lets you filter the size of images in the results, and the second lets you choose the content type. By default, both of these will be set to include everything.
The content type choices include news images, line art, photos, faces, and clip art. This is still an experimental feature, but it's still reasonably accurate, and it makes searching much faster.
