For the pumpkin cake: Spray a 12-cup Bundt pan with nonstick cooking spray. Preheat the oven to 350 degrees F.
In a large bowl, combine 2 boxes of the pound cake mix, 1 stick of the butter, 4 of the eggs, 1 can of the pumpkin puree and 2 teaspoons of the pumpkin pie spice. Mix with a handheld electric mixer on high speed until blended, about 1 minute. Pour into the prepared Bundt pan and bake until a toothpick inserted in the center comes out clean, 50 to 60 minutes.
Let cool in the pan for 15 minutes, then unmold onto a wire cooling rack. Repeat the process to make a second Bundt cake.
Once the cakes are cooled, level off the bottoms with a serrated knife so the cakes will sit flat. Place one of the cakes cut-side up and spread the vanilla frosting over it. Place the second cake, cut-side down, on top to form a pumpkin.
For the glaze: In a medium bowl whisk together the confectioners' sugar, cream cheese, milk and food coloring. (The glaze should be a bright orange color; add a few more drops of food coloring if needed.) The mixture will be very thick but still pourable. Place the pumpkin cake on a baking sheet fitted with a wire rack. Slowly pour the glaze over the top, moving in a circular motion around the top of the cake and letting the glaze drip down the sides. Set aside until set, about 1 hour.
Wrap some fruit leather around the green ice cream cone and press it into place upside down on the cake to form a stem. Dust a work surface with confectioners' sugar, place some fruit leather on top, and cut out a leaf with a leaf-shaped cookie cutter. Press the leaf into place on the cake near the stem.
For the graveyard: Spray an 18-by-13-inch baking sheet with nonstick cooking spray and line with parchment; spray the parchment.
Prepare both boxes of brownie mix according to the package instructions and pour into the prepared baking sheet. Bake according to the package instructions. Let cool completely, then remove from the pan and place on a large cutting board.
Frost the top of the brownie sheet with the chocolate frosting. Slice about 60 of the chocolate ladyfingers in half crosswise. Press the halved cookies, cut-side down, side-by-side around the top edge of the frosted brownie sheet to form a fence. On one of the long sides of the brownie sheet, leave a 3-inch opening in the fence to create an entrance. Place 2 whole ladyfingers on either side of the opening to form the gate entrance. Place another whole ladyfinger on top of the two ladyfingers to make the top of the gate, using a little bit of frosting to adhere it.
Cover the top of the frosted brownie with the crumbled chocolate cream-filled cookies to make dirt. Place the pumpkin cake in the center of the graveyard.
To make the gravestones, place the rectangular cookies and vanilla wafer sandwich cookies on a baking sheet lined with parchment paper. Spray both sides of the cookies with the silver spray food coloring.
Use a knife to cut slits into the brownie to hold the gravestones. Carefully place the gravestones into the slits.
Place the small candy pumpkins and marshmallow ghosts in the graveyard around the pumpkin. Serve immediately.