Add a surprising detail to iced sugar cookies using ordinary rubber stamps; the "ink" here is liquid food coloring. Choose one design or a few (you can also have stamps custom-made at an office-supply store). Make sure the royal icing is dry. Wet a piece of felt with food coloring; ink stamp on felt, blot on paper towel, then press gently on cookie. Dry one hour; seal treats in cellophane bags tied with twine.