For a snowmen cake, base ice a quarter sheet cake with white icing. Position a torn piece of paper towel on top of the cake, and airbrush blue around it to create the sky and clouds. If you are using buttercream icing, wait at least 30 minutes or until the icing has a skin on the top to place the paper towel and spray the color. If you are using a non-dairy icing, to avoid sticking, place a piece of netting or tulle on top of the icing, and then place the paper towel. To make the evergreen trees, dip a fan brush in green airbrush coloring and lightly draw the branches of the trees.