I've never noticed google crawling my images on other websites, is this what it does prior to putting them in image search?
64.68.87.43 - - [20/Sep/2003:03:58:12 -0700] "GET /galleries/Mindy2/300-0,022.jpg HTTP/1.0" 200 27980 "-" "Googlebot/2.1 (+
http://www.googlebot.com/bot.html)"