Instead of a salad bar, how about offering something completely different: perhaps a soup and bread bar?
Offer it as either a stand alone option or as part of a full course meal.
Have at least three different soup options, and a variety of breads / rolls.
However, properly implemented, a salad based meal, standing alone, is tough to beat.
see:
http://www.souplantation.com/
So much hunger in the world, and so many different ways to satisfy it!