1Bring water to a boil; add shrimp, and cook 3 to 5 minutes. Drain well; rinse with cold water. Chill. Peel and devein shrimp; set aside.
2Prepare the rice according to the package directions, omitting the butter. Combine the rice, vinegar, and next 4 ingredients; stir well. Add reserved shrimp, chicken, tomato, peas, celery, onion, and pimiento; toss well. Cover and chill thoroughly.
3Serve the salad on lettuce leaves on individual salad plates. Garnish, if desires with lemon slices.