Windows 10 has greatly restricted how much users can personalize the appearance of the OS. Themes aren’t what they used to be and it was only after users complained did Microsoft bring back the colored title bars. Many customization options that were accessible from the Control Panel have been hidden and setting a desktop background is now something you can only do from the new Settings app. This has a major drawback; the Settings app doesn’t let you set a different wallpaper for multiple monitors and there is no visible way to do it from the Control Panel. Fortunately, there’s a very easy work around to it.
Open the Run box using the Win + R keyboard shortcut. In the box paste the following and click enter.
control /name Microsoft.Personalization /page pageWallpaper
This will open an instance of Control Panel to a very specific section that you can’t get to otherwise from the Control Panel app.
In this section, one image which is the current desktop wallpaper will appear and it will be selected. From the ‘Picture location’ dropdown, select where you want to get wallpapers from and load the images. All images from the source you specified will be selected when they are first loaded. Clear the selection using the ‘Clear all’ button and select the one image you want to use. With the image selected, right-click it and choose which monitor to set it for. Repeat for the second monitor. The backgrounds will update in real time and the Taskbar that appears on the two monitors will likewise be of a different color (depending on the color settings for the Taskbar).
There should definitely be a more obvious way to do this and it makes absolutely no sense for Microsoft to hide the functionality.