As I noted yesterday in my Windows Phone 8.1 Preview, Microsoft is adding the ability to customize your Start screen background with a favorite photo or other image. But this doesn't work as it does in .1, and the background photo bleeds through the tiles, not the surrounding area. But as this video reveals, it also comes with a neat animation effect when you scroll through the screen.
I shot this very short video at yesterday's Nokia NOW press event. But I think it neatly highlights how well this new capability can work if you choose your picture—and tile placement—properly.