It's called Lively Wallpaper. For most people ... including the ability to pause while you're gaming, to speed up to slow down depending on what you're doing and to disable when you're connected ...

For adding custom background images: in lively right-click on the wallpaper and select "open file location" copy the image into the "images" folder in lively right-click the wallpaper and select ...

Lively supports running wallpaper as Windows Screensaver. Works with all wallpaper types (videos, picture and gifs, webpages..) Think of Lively as a powerful screen saver manager with modern features ...