Google Image Search could be used in many ways.
1. If you want to know if a person is a man or a woman and the name doesn't help, do a search for the name.
2. If you don't know the meaning of a word, the pictures may help you.
3. A better search for Flickr. Google uses information from other sites that link to Flickr photos, so you may find Google search better.
4. Find what's interesting about a site, by looking at the pictures included. For example: wired.com.
5. Find a new wallpaper for your desktop by restricting your search to large images. You can automate this using an application.
6. Find random personal pictures, using standard file names from digital cameras.
7. Type the name of a painter and you can take an art class.
8. Install a Greasemonkey script so you can view the original version of the image directly by clicking on the thumbnail.
9. Find the color of a word. "Word Color is a windows program that uses Google Image Search to determine the color of a word or string of words. It goes out there, retrieves the top 9 images and loops through all pixels, calculating the average hue, which is later converted to a color."
10. If you want to grab search results, GoogleGrab is a tool that downloads images from Google Image Search. It even supports batch search.