I think there are several methods but frankly, other than watermarking and digitally signing the images, I'd not bother. Unless you have a team to help to do the rest of the solutions, it just isn't time practicle for one person operations. For every method there is a counter to it, and no its not giving in either. Its business sense. Watermarking helps in advertising so there is that gain, but eventually we'll have digital encoding that's easy to install, easy to track and easy to prosecute the thieves.