This greeting card site is using my shamrock image (fourth in the first row, also in an edited version as the first image):

http://www.greetingstar.com/index.php?action=catalogue&cat=335

This sucks. All I can do is to ask them to have it removed, I guess.

Why not ask them where they purchased your images with a license to resell like this?  Then send them an invoice for the appropriate license or get the site to peruse it.  SS have taken legal action and compensated me twice in the past.