A shell border can be as simple as icing alone, or intersperse each icing shell with confetti sprinkles, candy-coated chocolates or other mini candies.
Starting at outer edge of flower, pipe shell with elongated tail towards center of flower. Repeat, adding additional petals. Add confetti sprinkle, icing dot, swirl or star flower center.
Two shells, when angled just right, make a fanciful icing heart.