This has been brought up before, and I suggest anyone remotely interested in techniques for watermarking/stamping use the SEARCH feature at the bottom of the forum page to look for these threads (you can search by 'watermark', 'branding', 'stamping' or by author - oion, since I was involved in at least a few of them). Unfortunately I removed the demo images.. It's not foolproof (depending on how you do it), but can save a bit of headache/heartache later.