3. Change the Display for the playing wallpaper.

There are three options for choosing Display.
1. Selected screen only: if you have one more display, you could select one which you want to display the wallpaper. the other one will not play.
2. Span accross screens: if you have one more displays, you could play the wallpaper accross the other screen.
3. Duplicate the same wallpaper: duplicate the wallpaper to the other screen.