Chris is right. Because of the way information is delivered to a
browser, any browser, it is not possible to stop a picture from being
saved. The picture is delivered as is to the browser by the server.
Applies to all browsers. You can do some things to slow down the
honest people from copying them such as creating your own right click
events (so someone cannot access the save as function from there).
Unfortunately the picture is already in a caching folder/file on the
machine that is using the browser. Someone fimiuliar with where they
are kept can always get to them despite your best efforts. In short,
the people who want to steal them are going to no matter what you
do.
Your best bet is to watermark the pictures prior to posting them. A
visible watermark deters people from stealing as it makes the picture
unusable for thier purposes or to much work to fix it. A watermark
that is invisible to the naked eye can be tracable should you need to
lodge a legal challenge to someone who is using your material without
authorization.
I know of no other methods for protecting yor work.
Sorry,
BWKing