...but what if each of those jigsaw piece images was like an animated gif which very briefly flashed something else. If all the images very briefly flashed out of sequence you might be able to prevent a screen grab capturing the whole image. If every time you screen grabbed the image, ten random pieces of the jigsaw were say, a randomly multicoloured square, then it could make getting the image so tedious most perpetrators would give up. I don't know if you could flash the squares quickly enough to prevent it ruining the image to the observer. I know, I know, probably not worth the effort but the idea stimulated my little grey cells.