Set a Wallpaper in the Settings App on Windows 10 To change desktop backgrounds individually for each monitor, head to Settings > Personalization > Background. Under Choose Your Picture, right ...

Where do you find your multi-monitor wallpaper? No matter how well known or obscure your sources, we want to hear how you put a sparkle on your enormous bank of screen space!

Can't understand why Windows doesn't have better built-in dual monitor support like this. DisplayFusion is a free download (donations requested) which requires the .NET 2.0 runtime to run.