Combine the rice, milks, sugar, pumpkin, spices, vanilla, and salt in a heavy bottom saucepan. Bring the rice mixture just to a simmer; watch it carefully, because it will boil over given half a chance (and trust me, you do not want to clean that pot). Turn the heat down to low and stir the rice mixture well. Cover the pan most of the way and simmer the rice pudding gently for about an hour, stirring every 10 minutes or so to keep the rice from sticking to the bottom of the pot.
When the rice is tender, remove the pot from the stove and stir in the liqueur. Cover the pan and let the rice pudding cool at least 30 minutes before serving. Garnish as desired. It's best served slightly warm or at room temperature.