Use sugar ice cream cones. Stand each upside down on a sheet of waxed paper. If white icing is very stiff, thin about 1/3 cup of icing. Using a small spatula or back of a small spoon, spread icing generously over the sides of each cone, swirling surface of icing. If desired, decorate with small candies to resemble lights or balls. Immediately sprinkle with red or green colored sugar. Allow about 15 minutes for icing to dry before moving.