I tested it. rt click, 'save picture as' works fine. You said you were trying to prevent people from saving the picture? Back to the drawing board.
Basically, if you post it publicly, it is out of your control, unless you want to get involved in chasing down your pictures by doing track searchs looking for the ADS hidden streams embedded in the pic. Some image software allows for copyright labels to be embedded, like Corel, but otherwise, so if someone steals your work, you can always go after them with the proof. I always put some kind of visual copyright notice on the image. The key is to not post stuff publicly that you don't want to be distributed or if you do, be sure to id the pic and post an image use policy.
dogbert