Preheat the oven to 350°F. Spread the pecan pieces on a baking sheet in a single layer. Toast for 6-8 minutes. Set aside ¼ cup to garnish the top. Cool.
Meanwhile, prepare the cake per the package directions using the amount of eggs, oil and water called for on the box. Bake according to directions in a 13x9-inch baking pan. After baking cool completely then cut into 1-inch cubes.
In a large mixing bowl using an electric mixer, beat together the cream cheese, pumpkin, powdered sugar, pumpkin pie spice and vanilla. Whip for 2 minutes or until smooth, light and fluffy. Fold in one 8-oz whipped topping by hand.
To assemble, layer ⅓ cubed cake in the bottom of a large trifle bowl. Drizzle with ⅓ caramel sauce and sprinkle with ⅓ pecans. Top with ½ pumpkin cheesecake filling.
Arrange ⅓ cake over pumpkin filling, drizzle with ⅓ caramel sauce and sprinkle with ⅓ pecans. Spread with one 8-oz whipped topping.
Arrange final ⅓ cake over whipped topping, drizzle with final ⅓ caramel sauce and ⅓ pecans. Spread with remaining pumpkin cheesecake filling.
Frost the top as desired with remaining 8-oz whipped topping. Arrange Ginger Snaps on top and sprinkle with additional pecans or a dusting of cinnamon. Chill thoroughly for several hours or overnight.
Store leftovers chilled.