Using a sharp knife, carefully cut the lid off the pumpkin to create a wide opening. Scoop out the seeds with a large metal spoon to form a bowl, being careful to keep a thick layer of the pumpkin wall intact (see tip below for using the seeds).
To make the cocktail, mix together the coconut rum, pomegranate, orange and lime juices with the ginger ale in a large jug.
Fill the pumpkin bowl with ice and pour over the cocktail mix. Garnish with the orange slices and pomegranate seeds to serve.
