Christmas Tree Cupcakes: tint frosting green. Add to a pastry bag fitted with a 1M tip and frost cupcake high, then decorate with a gold star sprinkle and other sprinkles for ornaments.
Melted Snowmen Cupcakes: frost cupcake white. Cut a large marshmallow in half and place it on the cupcake. Place sprinkles as buttons facing away from the head and use a toothpick with food coloring to draw the arms and face.
Santa Hat Cupcakes: tint 3/4 of frosting red. Use a round tip to pipe the hat then use a star tip to pipe around the edges and the tip.
Pinata Cupcakes: tint frosting 2 or 3 colors. Wrap each color frosting in plastic wrap formed into a log. Place all frostings in a pastry bag fitted with the 1M tip. Cut out top of cupcake and fill with sprinkles. Frost cupcake.
See the recipe post for more details and links to tools and other resources.