keyplyr - 10:42 am on Dec 30, 2012 (gmt 0)
keyplyr - will that only block bing image or also google, because many dont want to block google (yet)
zeus - using a NOINDEX X-Robots-Tag HTTP header will not *block* anything, it will only tell the SEs (that comply) not to index your images. Sorry, it will tell Google and other SEs this as well.
There is not a mechanism to only tell Bing not to index images unless you cloak (deliver different responses to different UAs, which is taboo and if caught, could bring penalties.)
Robots.txt will only disallow images from being crawled (and thus indexed) if the SE does *not* already have your images. Adding a disallow for a certain bot in robots.txt will not remove any images already indexed. The only to do this is as I described above, using the NOINDEX X-Robots-Tag HTTP header.
Sorry, there is not a perfect solution.