I found this post on Blogstorm and it seems like a good idea. It's javascript code to gives users a small notification when they right-click on a photo. The difference between this and most right-click prevention tools is that this one encourages users to "steal" your images but requests they provide a link to your site. It even provides the code for them to do so. Here's the link:

http://www.blogstorm.co.uk/blog/use-google-images-and-hotlinkers-to-build-links/

Anyone have an idea how to change the code to make it work with vanilla?