Make fondant flower and skull one week in advance. Knead 1/8 teaspoon Gum-Tex into a 1 1/8 in. ball of white fondant. Use 9 in. fondant roller with pink guide rings to roll out fondant 1/16 in. thick. Use small rose cutter from set to cut one flower for each treat. Let dry overnight in 3 in. flower forming cup dusted with cornstarch.
Highlight flower and skull. In candy melting plate cavity, combine brown, blue and white Color Dust to make gray. Use brush and gray dust to highlight skull and flower.
Make cupcakes. Prepare batter following recipe directions. Bake and cool cupcakes.
Ice cupcakes. Prepare buttercream icing following recipe directions. Tint black. Use spatula and black icing to ice tops of cupcakes smooth. Use icing to attach skull to flower. Position flower on cupcake.