ccDan, what you are suggesting would be copyrightable. But it would not have the same strength as a copyright on a completely original work.
Let's say that you decided to tint the lips red and the eyes blue in an old black and white picture. You can copyright that work, but it is only the lip and eye tint that you have a copyright over. You would have trouble claiming infringement if someone takes your copyrighted modified picture and "transforms" it by tinting the lips orange and the eyes red. Your copyright is only in the changes you made.
True, but my main concern is that they don't exactly duplicate my work. Plus, if they were to do something as you've described, they would be better off working from the restored image (upon which there is no copyright claim or notice) rather than my altered image.
So, if the copyright notice serves to deter people from grabbing my altered image and sticking it as-is on their website, then it's done its job. How far I would go in trying to defend that copyright claim would depend upon a number of factors.