Legal Rulings On Image Search & Meta Tags
In the right circumstances, image search engines don't violate copyright
and using another company's trademarks in meta tags isn't infringement,
two separate court cases have found.

In the case involving image search engines, the US Ninth Circuit Court of
Appeals ruled this month that displaying thumbnail images of pictures found
across the web was fair use. However, it also ruled that it wasn't fair use
to link directly to images or to show them on their own, within a frame.
Instead, links need to be to the page containing the image, rather than the
image itself.
http://searchenginewatch.com/sereport/02/02-legal.html