Miniature chocolate and vanilla cupcakes surround white-fondant tiers speckled with piped Swiss dots. Brown-and-pink-hued paper flags wave from piped icing swirls; the flags on the cupcake at the top are calligraphed with the newlywed's names.
Trim all of the cake layers level. Frost tiers: Place 1 16-inch chocolate layer on corresponding-size foam board, and spread with 2 1/2 cups frosting. Top with 16-inch vanilla layer, and spread with 2 1/2 cups frosting. Top with remaining 16-inch chocolate layer; coat top and sides with 3 cups frosting. Refrigerate until frosting is firm, about 2 hours. Repeat with remaining layers, foam boards, and frosting. For the 12-inch tier, use 1 1/2 cups frosting between each layer and 3 cups to coat top and sides; for 8-inch tier, use 6 tablespoons frosting between each layer and 1 1/2 cups to coat top and sides; for 4-inch tier, use 2 tablespoons frosting between each layer and 1/2 cup to coat top and sides.
Cover tiers (see Cook's Note for fondant amounts): For each tier, roll out fondant to 1/8-inch thickness. Drape fondant over a rolling pin; center and place it on the tier. Starting at the top, smooth fondant onto cake with your hands. Cut away excess with a pastry wheel. Tiers can be stored in the refrigerator up to 24 hours.
Assemble tiers: Center the 16-inch tier on the cake board. Insert 8 dowels into 16-inch tier, arranging 1 in center and the rest evenly spaced, about 2 inches from edge. Mark top of cake on dowels; then remove, trim, and reinsert them. In the same way, insert 5 dowels in the 12-inch tier, and 4 dowels in the 8-inch tier (1 in center and the rest evenly spaced, about 1 1/2 inches from edge). Stack tiers largest to smallest. Decorate with royal icing as desired.
Place 3 3/4 cups frosting in a pastry bag fitted with a small star tip (such as Ateco #18). Pipe frosting decoratively in a swirl on cupcakes. Alternate mini chocolate and vanilla cupcakes around lower tiers; place standard-size cupcake on top tier.
Fondant amounts for each tier: 4-inch: 1 pound; 8-inch: 3 pounds; 12-inch: 4 1/2 pounds; 16-inch: 6 1/2 pounds.