How Do I Delete My Picture From Google Images?

http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=35308

Here is an excerpt:

To remove an image from Google's image index, add a robots.txt file to the root of the server that blocks the image.

For example, if you want Google to exclude the dogs.jpg image that appears on your site at www.yoursite.com/images/dogs.jpg, add the following to your robots.txt file:

User-agent: Googlebot-Image Disallow: /images/dogs.jpg

To remove all the images on your site from our index, place the following robots.txt file in your server root:

User-agent: Googlebot-Image Disallow: /