1. Preheat oven to 375°F. Grease and flour two 8-inch round cake pans.
2. Combine cake mix, eggs, water, pumpkin, 1 teaspoon cinnamon, ginger and nutmeg in large mixing bowl. Beat at medium speed with electric mixer 4 minutes. Stir in 1 cup walnuts. Pour into prepared pans. Bake 30 to 35 minutes or until toothpick inserted into center comes out clean. Cool in pans 15 minutes. Remove from pans. Cool completely.
3. Combine frosting and remaining 1/2 teaspoon cinnamon. Stir until blended. Fill and frost cake. Garnish with 1/4 cup walnuts.