Windows 10 by default can only be set to have 1 image to span all screens. Windows 7 was like that as well. 8-10 have the option for individual images or a single spanned. When setting wallpaper, all you have to do is right click and it shows set to all monitors or set to monitor 1, 2, etc. This hasn't changed any since release for 10. 8 has a different control panel to do it. 7 could never do individual without a 3rd party like ultramon.