some kind of green salad- you might take a look at the Greek village salad on the salads that hold page- scaled for 100, use 1 1/3 to 1 1/2.
a marinated vegetable salad such as the antipasto vegetables on the appetizer page, or a marinated bean salad such as the 3 bean type salad, maybe with grape tomatoes stirred in for color and texture. about 4 gallons.