Here is an article on making your own mark. If you place the mark in an inconspicuous part of the image which can not be easily cropped it adds some protection. I made one I use at times but I'm not totally pleased with it yet.
How-To: Creating Your own Chop http://www.creativepro.com/story/feature/18343.html My present version is used here: http://members.shaw.ca/hargravep/Image5.htm Powell
