Heat oven to 350°F. On ungreased cookie sheet, place cookie dough rounds 2 inches apart. Bake 12 to 16 minutes or until edges are light golden brown. Cool 2 minutes; remove from cookie sheet to cooling rack. Cool completely, about 10 minutes.
Meanwhile, in medium microwavable bowl, microwave 1 cup of the white vanilla baking chips uncovered on High 45 seconds. Stir; if necessary, microwave in 15-second increments, stirring after each, until chips can be stirred smooth. Cool 5 minutes. Stir in frosting until well blended. Reserve 2 tablespoons of the frosting mixture to attach decorations. Use gel food colors to tint remaining frosting in desired colors. Spoon each color of frosting into resealable food-storage plastic bag. Cut 1/2 inch off one corner of bag, and pipe on bottom of 1 cookie. Press another cookie, flat side down, on frosting at an angle, cookies touching on one side and about 1 inch apart on the other, to look like open mouth.
To decorate, press remaining white vanilla baking chips in frosting for teeth. Use reserved frosting mixture to attach eyes, using decorations as desired.