이미지에 대한 컨트롤..

http://cafe.naver.com/goorume/608

As an alternative to...

newImage.src = "http://localhost/image.jpg?" + new Date().getTime();

...it seems that...

newImage.src = "http://localhost/image.jpg#" + new Date().getTime();

...is sufficient to fool the browser cache without bypassing any upstream caches, assuming you returned the correct Cache-Control headers. Although you can use...

Cache-Control: no-cache, must-revalidate

...you lose the benefits of the If-Modified-Since or If-None-Match headers, so something like...

Cache-Control: max-age=0, must-revalidate

...should prevent the browser from re-downloading the entire image if it hasn't actually changed. Tested and working on IE, Firefox, and Chrome. Annoyingly it fails on Safari unless you use...

Cache-Control: no-store

...although this still may be preferable to filling upstream caches with hundreds of identical images, particularly when they're running on your own server. ;-)