I had that problem at first. I like to use my own pics for wallpaper. At first, I picked 3 pics from my gallery, then selected what I thought was one of them for my cover screen wallpaper just to try it out. But, I apparently had selected all 3, so I got the same result as you. I went back in to the cover screen settings and then selected only one pic. So, all I can say is be sure that you have selected only one picture for your wallpaper.