How do you make it so that no one can copy your pictures from your website?

As you know, the easiest way to download images is by right-clicking on them and selecting "save image". So you can disable this capability, to put off less web-savvy image thieves and people who can't be bothered with the hassle of looking at your HTML or searching the browser cache. If you're running a Wordpress website, the No Right Click Images Plugin could help you with that.