Thanks Mike. One thing about this image is that all the stones are individually modeled. It is not just a plane with an image applied. The mortar between the stones is a plane so the mortar can be any color or texture. It was a lot of work, but for a newbie it was good simple modeling experience, which I needed.
Anyway, I took your advice and turned up the normals on the stonework. I also changed the modifier on the stonework from subsurface to bevel.
I blurred the trees and the grass also. It looks a little better, but the castle still seems to “float” in the image rather than being a part of it.