Hmm, ugly as it seems, wrapping the image in an Applet or Flash movie may be your best option. It might not stop people getting the image by taking a screen-dump, but you'll never stop someone if they're prepared to go to extreme measures. For example, if you put it in an Applet then the Applet requests and displays the image, if the user sets up their own proxy they can see or intercept the image. If you put it in the same jar as the Applet they can still get the jar and open it manually. Trouble
I know this is an old post, but you might want to have a look at this. Anti-Leech is what you want. You can protect quite a bit of information on your web page, including: js, HTML, Images, Documents, etc. I can't believe someone else said this can't be done. And a bartender no less.
Any image on a webpage is saved in the temp. internet files. This means there is always a copy o iy in the webpage. The only way to protect an image is to put your logo on it, or take your harddrive and burn it and scatter the ashes in the ocean.
I'm not sure if I approve of this interruption. But this tiny ad checks out: