Bring 3 quarts water and 1/4 cup Old Bay seasoning to a boil in a Dutch oven; add shrimp and cook, stirring occasionally, 2 minutes or until shrimp turn pink. Drain. Pour shrimp into a 13- x 9-inch pan to cool. Peel shrimp, and devein, if desired; chop shrimp.
Stir together celery and next 5 ingredients; stir in shrimp. Cover and chill 2 hours. Serve on lettuce leaves with assorted crackers, if desired.
Shrimp Rolls: Place 1 lettuce leaf on top of each 8 (8-inch) flour tortillas. Top each evenly with 1/2 cup Old Bay Shrimp Salad and 3 or 4 avocado slices. Roll up tortillas, and secure with thick, round wooden picks. Cut in half. Makes 8 servings.
Shrimp Pitas: Cut 12 mini pita pockets in half. Stuff pockets with Old Bay Shrimp Salad. Makes 8 servings.