1. Spread 1/3 cup Chicken Salad evenly on 1 side of 3 bread slices. Stack Chicken Salad-topped slices; top with 1 bread slice. Repeat procedure with 4 more bread slices and Egg Salad. Repeat procedure with remaining bread slices and pimiento cheese. (You will have 3 stacked sandwiches.)
2. Beat cream cheeses and milk at medium speed with an electric mixer until smooth. Spread evenly over top and sides of each stack. Cover and chill at least 1 hour or up to 24 hours. Garnish chicken salad sandwich with celery leaves, egg salad sandwich with paprika, and pimiento cheese sandwich with Cheddar cheese, if desired.