The prize sticker is for a book cover I entered in the Mystic Book Club's graphics contest. You can see it on this page:

https://www.wattpad.com/1463431151-art-graphics-mystic-book-club-graphics-contest-1

and here:

https://www.wattpad.com/1470787894-%E2%95%B0-winners-%E2%9C%A7