On July 20, 2017 going to release in Japan on Nintendo Switch the popular Fate game the Fate/Extella. The game going to release in Europe and North America on the same week but in Japan you can get with the game your limited smartphone wallpaper.
If you visit one of the official retailer store and scan the QR code from the right bottom part of the package cover you will be redirected to a special page and you can download your limited smartphone wallpaper.
The campaign started today and will be held until July 23, 2017. You can find the store list (Japan) on the official website of the game.