Preheat oven to 350°F / 175°C. Line the bottom and the sides of a 9" (23cm) springform pan with parchment paper by cutting out a circle for the bottom and strips for the sides. Set aside.
Gingerbread Crust: In a large bowl stir together cookie crumbs and melted butter until combined. Add sugar and salt and stir until evenly moistened. Transfer to the prepared pan and press crust into the bottom and halfway up the sides with the back of a flat-bottomed cup. Freeze until filling is done.
Eggnog Cheesecake Filling: In a large mixing bowl, using a handheld or stand mixer fitted with a whisk or paddle attachment, beat the cream cheese, sugar, and flour just until combined no lumps remain. Add nutmeg, cinnamon, vanilla, and rum and stir to combine. Add one egg at a time and mix just until combined before you add the next egg. Scrape down the bowl and add eggnog and mix until smooth and combined. Don't overmix at any step. Too much air in the filling can cause cracks while baking. Pour filling into the crust. Spread evenly. Place a piece of parchment paper under the springform pan and bake for 50-60 minutes until the edges look puffed and browned. The center should be very bright and almost set with a 2-3 inches wobbly spot in the center. Don't overbake because this is a common reason for cracked cheesecake.
Turn off the oven, crack open the door (pinch a wooden spoon), and let the cheesecake in the oven for another hour. Then remove from the oven and let cool to room temperature. Refrigerate at least 3 hours or overnight. Top with whipped cream and decorate with Gingerbread Men Cookies before serving, if desired. Store leftovers in an airtight container in the fridge up to 3 days.