In Windows 10, you can set a different wallpaper ... will appear on your monitors. While you have multiple displays set up, you'll also be offered a new fit option — "Span." ...

You will learn how to Center, Fill, Fit, Stretch, Tile, Span ... your wallpaper as it may perk up your mood as soon as you turn your computer ON. Read: Where are Wallpapers and Lock Screen images ...