But, isn't what constitutes "originality" somewhat subjective?
I use public domain images on my web site. In most cases, I have two versions available. The first is a restored image. In other words, I scan it in and I try to get it to look like the original, or what the original would have looked like if it had not been torn, faded, etc. I don't claim a copyright on that.
The second is an altered image. I may do special effects, change colors or colorize, and generally adjust the image to achieve a specific look. That, I stick a copyright on and notate that that particular image is an altered image.
Typically, too, the restored image is a higher resolution. So, I'm not preventing anyone from making use of public domain materials, though it would be nice if they credit me as the source for the image.
With the altered images, I am not trying to create an accurate representation of the original but rather a certain look to go along with my website design. With some altered images, there is no doubt that the changes constitute originality. With others, it might be more subjective. I think that I am adding originality to the work, as I am not simply doing repair or restoration, but rather trying to get the image to look a certain way. Restoration may be "sweat of the brow" but wouldn't trying to achieve a certain look be a creative process?