Why not make a lovely image like the one below for your desktop.
Go to the link, scroll down and select the icon that’s appropriate for the device you want to put the wallpaper on, PC or phone, pick the correct resolution, and the rest is basically you choosing the sprites/blocks you want to place in the level and building it however you want, much like it works in the actual Super Mario Maker game.
Yeah, it’s currently only available in Japanese, but you’re smart. I know you’ll figure it out.
Go at it and enjoy. 😀