If you are on Apache servers, you can add a line to an .htaccess file in the directory where your images are:
Header append X-Robots-Tag: noindex
to prevent your images from being indexed (in the future, anyway). This adds a noindex metatag to your images AND any other files in the directory served by that .htaccess file - so it is not for your site's .htaccess file or all your files will be noindexed.
22.214.171.124 - - [24/Jan/2013:08:12:53 -0700] "GET /pop.js HTTP/1.1" 200 596 "http://www.example.com/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.4 (KHTML, like Gecko; Google Web Preview) Chrome/22.0.1229 Safari/537.4"
Look at your raw access files and you can see for yourself.
EDIT: @ HuskyPup - Maybe they mean they will no longer be doing this iframe loading with their new implementation (?) that would give you more control and if they are loading from their cache then I will unblock their preview acess. It would be nice to know when they plan to do this?