By now, if you are still seeing the same picture on both of your screens you are missing out on something you might very well enjoy.
If you have an album of nice pictures that you can use, you can easily set the background as Slideshow and Windows 10 will take care of the rest, randomly pick two different pictures from your album and place them on both of your monitors. If you have 3 or screens, you will see 3 or more different pictures across all screens.
Right-click on the desktop and choose Personalize.
And then select Slideshow as the background and select the album via Browse.
Better yet, how about automatically save Windows Spotlight pictures and Bing images as desktop backgrounds?
Now what if you only have two pictures you like and would love to set them up on your screen side-by-side?
Easy, highlight the images you like to set as wallpaper, right-click on any of them and choose Set as desktop background.
Lastly, while we are on the topic of setting up a beautiful desktop background, here is a bonus tip. Wallpaperhub has some really gorgeous background set you might really like. The Surface Laptop feature pack looks just awesome.