I might try embedding meta tags - these are searchable and traceable. there are also many forms of copyrighting images of which you can read more about here:http://creativecommons.org/
you don't state which copyright you are allowing such as All Rights Reserved or Attribution 3.0 Unported
also, embedding the images as BBCODE here vs. a straight upload would allow your web site to track an IP address when someone clicks the image. This is a just in case you feel someone stole your work vs. here where you are not an admin and have no access to IP logs.
The heavy watermark embedded in these photos is not a safe secure way of protecting your work and may cause the interested party to look away vs. stare at the image as the watermark (as others state) is a bit obtrusive.