Cook egg yolks, sugar, salt, vinegar, pineapple syrup and butter in double boiler until thick. Cool.
Fold in whipped cream, cherries, grapes, marshmallows, pineapple, and oranges. Chill 24 hours.
Decorate top with orange sections, half slices of pineapple, and long stemmed maraschino cherries, if desired. Makes 6 to 8 servings.