I have thought about watermarks but to be honest they spoil the enjoyment for genuine users. I have put a copyright logo (small) on each picture. I have just loaded a plugin called ‘Content Copy Protection & Prevent Image Save’ from the wordpress.org site, almost full stars and it seems perfect. It stops you dragging the picture, right clicking, save as etc, brilliant. Having had pictures in the past stolen and used again (without crediting me) from flickr, I really wanted to protect them on my own site. Yes you can screen grab them, but they’ll never be as good as the originals.