look, the major u can make a <div> on the document with a transparent gif and then using css u can use a background for that <div> with the real image. that disables copy paste but not the Print screen. i just thought i could use the flash as the background and use actionscript to disable printscreen (when the user presses that key the flash switches to a black frame). but i dont know if its possible...
And... of course its impossible to prevent anyone from stealing images. but at least it would make it harder to do so. and i think flash as a no cache feature (someone told me)