For this cake, I prepared the frosting without adding the cocoa and removed a heaping cup of frosting to tint to use for the pumpkins (white and orange, and a small portion green)
In the bowl of a mixer, blend the butter and cream cheese. Add in the powdered sugar and heavy cream, mix until smooth, and add a tablespoon or two of heavy cream and mix until creamy.
Remove the portion for pumpkin decorations. Place some white frosting in a bowl, a portion for the orange, and add a small amount of cocoa or a tiny drop of brown with orange food coloring to make a nice warm orange color. Make a very small portion dark army green for the vine. Place the colored frosting into piping bags fitted with piping tips (#32 for the orange pumpkins, #4B for the larger white pumpkins, and #3 for the green vines).
To the remaining frosting, you'll add the cocoa, then add the vanilla and additional heavy cream, and mix well until the frosting is smooth, creamy, and spreadable. Remove a tiny amount of the vines on the pumpkins.
You'll then spread some chocolate frosting in between the cake layers. Spread more frosting on the sides and top of the cake. Make swirls with the back of a spoon in a swooping motion. Then pipe the "pumpkins" onto the top of the cake, add vines, and use a tiny amount of chocolate frosting for the vines. Refrigerate the cake to set the frosting.
Remove cake from the fridge at least an hour before serving.