If the lettuce is not prewashed, rinse it, drain, and spin or pat dry. Place a lettuce leaf on each serving plate.
Peel the eggs, place them in a 2-quart or larger bowl, and chop them fine, using two sharp knives or a chopping utensil. Add the mayonnaise, Thousand Island dressing, lemon juice, Worcestershire, onion powder, and pepper. Stir well to mix.
Reserve 4 whole shrimp for garnish. If the remaining shrimp are large, use kitchen scissors or a sharp knife to cut them in half or into bite-size pieces. Add them to the bowl. Cut the celery into medium-size dice and add it to the bowl. Finely mince the onion (if using) and add. Stir well to mix with the dressing, seasoning with salt. Top each lettuce leaf with the salad, dividing evenly. Garnish each salad with a whole shrimp and serve.