If there is any meaning to general spirit photography Dawn, then I think it would be just to be seen and recognised. Spirit is just everywhere to be seen, if one has the sight to see and register it.
I have looked at very old photographs and still see the same type of images we see today.
I really think spirit just wants to say "hey we are here, open your eyes and see us"! cheer

I do believe though at times, certain images, faces, messages, do appear just for the person who is present/taking the photograph. wave

Dreams are different as they are obviously personal to us and we experience them in a different state of consciousness than when we are awake and are taking photographs( at least I think I am awake!! hahaha)
hysterical