In a large bowl, dissolve gelatin in boiling water. Add tomato sauce, vinegar, Worcestershire sauce, salt and pepper and mix well. Cover with plastic wrap and refrigerate until partially set partially set.
When partially set, fold in celery, green onions and shrimp.
Spray a decorative bowl lightly with nonstick spray. Fill with gelatin mixture, cover with plastic wrap and refrigerate until set.
To serve, unmold on bed of lettuce and garnish with mayonnaise.
Instead of using a mold, pour into lightly sprayed 8-inch square pan, cover and refrigerate until set, and cut into squares to serve.