Decorate cake. Prepare buttercream icing following recipe directions. Tint portions royal blue (for light blue), royal blue/black combination (for dark blue), black and red-red/Christmas red/black combination (for red). Reserve remaining white. Use spatula and blue icing to ice cake sides and background areas around face smooth.
Use tip 3 and black icing to outline Spider-Man face. Use tip 16 and black icing to pipe stars for eye borders. Use tip 16 and white icing to pipe stars for eyes. Use tip 16 and red icing to cover face with stars. Use tip 6 and dark blue icing to outline web.