What is featured on the album cover of the best-selling 12" signle of all time?
Better Living Through Chemistry (album):  The album cover features an image of a 3.5-inch floppy disk, paying homage to the cover of New Order's "Blue Monday" single, which featured a 5.25-inch disk. Blue Monday (New Order song): "Blue Monday" is a song by the English rock/dance band New Order. Blue Monday (New Order song):  It is the best-selling 12" single of all time.
5.25-inch disk