I find watermarking something more than just art protection. I find it really fun to design watermarks or logos which are not just a watermark but also become a nice part of the picture. So I finally designed a universal symbol of myself as an artist. I will be putting this symbol into my pictures so they could be easily identified as my art. They will be often very hard to notice without searching for them~ I think that this is a good backup way to protect your art from theft.