Add to a large pitcher the white grape juice and pomegranate juice. Pour the juice into 1 muffin tin, filling the cups half of the way up. Drop a few fresh raspberries and pomegranate seeds into each muffin cup and place in the freezer until frozen.
Place the pitcher with the remaining juice in the fridge until ready to serve. Right before serving, pour the juice into a punch bowl and top with ginger ale and prosecco.
Remove the muffin tin from the freezer and remove the ice cubes with a small spatula; let sit out for a minute if they don't pop out. Add ice cubes to punch bowl and serve!