One day in advance, make mini cone hats. Holding cone at tip, dip cone into cup of water, leaving 2½ in. of cone at tip dry. Hold for 10 seconds. Using knife, trim cone at water line. Repeat for 24 hats.
Place desired sprinkles in shallow bowls or plates. Using spatula, lightly ice cones with royal icing; immediately coat in sprinkles until cone is completely covered. Set on waxed paper to dry, about 1 hour.
Using Black icing color, tint ¼ cup royal icing black. Prepare 12 in. disposable decorating bag with tip 1 and black royal icing. Pipe messages on cones. Let dry, about 30 minutes.
Prepare 12 in. disposable decorating bag with tip 16. Pipe tops of hats; immediately cover with sprinkles. Pipe zig-zag along bottom base of each hat; immediately cover with sprinkles. Let dry on waxed paper, about 8 to 10 hours.