Peel and section oranges over a small bowl to reserve juices. Stir sugar and rum, if using, into orange juice until sugar is dissolved. In a large mixing bowl combine the orange sections, pineapple chunks, star fruit slices, and mango and/or papaya slices; drizzle with orange juice mixture. Stir gently to coat. Cover and chill for 1 to 24 hours, stirring gently once or twice.
To serve, arrange a long slice of papaya in each dessert dish. With a slotted spoon lift fruit mixture into dishes atop the papaya slice. Top with whipped cream and sprinkle with toasted coconut. Makes 6 to 8 servings.