You can't possibly come up with enough methods to stop a determined thief. If they want it, they'll get it. Spending time and money trying to defeat a thief is a waste of time and money. Spend your time and money making life better for your valued customers. You don't have to make life easy for a thief, but don't waste money on gadgets, scripts, products, software, or any other tomfoolery.
Increasing "security" could very easily alienate your legitimate users, and those are the people that keep your business alive.
What you can do is NOT post full size images to a website. Keep the resolution to a minimum, yet high enough to be effective. 640x480, or 800x600 on a web page is probably just fine.
Most people will not steal your work because most people are honest.
Actually, to tell you the truth, most people will not steal your material simply because they aren't interested in your material. I don't mean to insult you, but if you had a large paying client base, you wouldn't be here asking these questions.
Good luck.
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'In 1983, the game of golf had a firm grip on the waist of my boxers and was administering the death wedgie. I had a dose of the atomic yips and after missing 10 of 11 cuts by a single shot, I was ready to quit and apply for a job as a wringer-outer for a one-armed window cleaner.'