Search engines no longer use keyword meta tags, because the system became too easy to abuse. We removed this aspect of the sites when the last remaining search engines stopped checking meta keywords. Because people were spamming their keywords with inappropriate and inaccurate terms, search engines now use smarter ways to build their indexes.
Here are a webinar that helps clarify the issue:
http://www.mattcutts.com/blog/keywords-meta-tag-in-web-search/
It is much better to include relevant words, such as your name and what you do, in the natural language visible on your website, as well as the 'Caption' area we provide for each image, which you'll see on each Image Page in your Control Panel. Caption text is a relatively new partial replacement for keyword meta tags, and describing your image in this section in natural and honest language can help your site's ranking in Google, as well as helping to get your images to show up in Google Images. Captions are also cool, since they can be read aloud by web browsers for the visually disabled.