One thing that I think sets the gnome desktop behind the others is the lack of adding directories for wallpapers. Instead of grabbing photos from just ~/Pictures, perhaps allow it to grab from sub-directories in ~/Pictures too? And also to add custom directories. On top of that, it would be nice to have a rotating wallpaper feature in the gnome desktop too. I like the minimal looks for wallpaper selecting, but there really needs to be more diversity than just "pick stock photos or only photos from ~/Pictures"