@Cooloring if on a pi 3, disable overscan on /boot/config.txt.

If on a pi 4, doesn't work with omxplayer because of different video handling. Use VLC for screensaver.

You may choose to use VLC for screensaver on the pi 3 as well, but performance isn't great.

You can do it on Attraction Mode and its cool,I use videos in it,but its a good idea,I don't see why Emulation Station couldn't do it.

Sorry for the shameless bump, i am just desperate to change the screen saver to a company logo!