I agree with Tobbo, the best way to combat this is to post your art everywhere. The more people that have see your art, the more likely stolen works will be recognized. You could try to do some universal branding, like a giant logo in the background that's barely visible. Name your images with your name in it, if someone…
There is a way to add some copyright protection to your rendered images. This can be easily removed, but if a novice is willing to steal another artists' work and pass it off as their own, they might just overlook these simple protection measures. Step 1: Open your image in Photoshop and click on "File Info" in the File…