if you have Windows 10 build 10525 or higher. Images won't change when you're running on battery unless you go into the advanced power settings for your power plan and change Desktop background ...

Windows 7 comes loaded with an array of visually appealing desktop background images, and many more background images are available online. If you allow anyone to make changes to your computer's ...

including the start screen and desktop background images that Windows 8 ships with and also a set of wallpapers that Stardock ships with the app. You get the usual fill, fit, tile and center ...