In my opinion, it's an uphill battle that can't be won. There are just too many techniques that are used to beat image theft protection. I think the only alternative would be to have a visible marking upon all the demo pictures, of course this may come across as gawdy to some and even unprofessional perhaps. It would take a long time to prep 500 images. Even at that, it would only take someone good with a image program to wash those away... but, it would provide a good deterrent. I know I can take whatever image I see over the net by various methods and it's all common knowledge to mostly everyone that's even semi-computer literate.
Theft of materials over the Internet has and always will be a problem. I had the odd poem of mine stolen from a poetry forum. All too easy, but I couldn't do anything about it... it's just text. Sure, I could copyright everything, but I don't have the time to scour the web to get into a long legal battle with someone on the other side of the world.
Like graphic/art websites... people like to show off their talent and obviously, you can't have a huge anti-theft marker across the whole image, so people steal them and blot out the artist's signature. What can you do?? Unless, there is some mega script that can disable screenshots, caching, and other various methods from all browsers and image devices... I don't see a relative solution to the problem. :no: