Funny, no one else has encountered this behaviour?
I deleted all the photos and then went to the website that has the picture I want to save to my iPad. I click and hold on the photo until I get the menu and then 'Save' the photo again. I think it's a PNG with a transparent background.
When I go to my photos, the thumbnail still shows another picture in the background, but when I open the photo, it disappears. When I close it, the thumbnail shows the background picture again. The background should be transparent even in the thumbnail... It likely is, but another thumbnail is showing through for some reason. I can tell because it's not as clear as the photo I saved, and appears only for a split second when I open it.
Seems to pick the 'background' randomly, but what I found weird is that it even shows pictures that have been deleted.