Cut up half of the banana and place in a blender. Slice the remaining half into 8 slices; set aside. Add creme de banana liqueur, rum, whipping cream, and 1 tablespoon of the ice cream topping to blender. Add ice cubes. Cover and blend until smooth.
Drizzle remaining 1 tablespoon ice cream topping onto the insides of eight 2- to 3-ounce glasses. Pour banana mixture into glasses. If desired, sprinkle with freshly grated nutmeg. Garnish each glass with a banana slice. Makes 8 (1-1/2-ounce) servings.