Slideshow period setting broken for manual uploads

I have 7 images that I use for my background and they are all manually uploaded (Background -> Upload). I want to change the slideshow period setting from the default 6 hours to 1 hour, however when I change the setting and press apply selection the setting does not work properly. If I then go back to the slideshow period setting it will still say 6 hours even though I changed it to 1. If possible, I would like there to be a random image option so that every time I refresh the new tab page the background image will change.