From the USPS, November 22nd, 2016:
The U. S. Postal Service celebrates our nation passion for athletics with Have a Ball! The stamps feature colorful illustrations of eight different sports balls: baseball, basketball, football, golf, kickball, soccer, tennis and volleyball. Millions in the U. S. participate annually in the sports represented on the stamps. Mike Ryan designed the stamps and Greg Breeding served as the art director. Daniel Nyari created the colorful, stylized stamp art.