We did 100% FREE showings, once per month on a Saturday Morning. Lasted 4 months. The first one was "The Goonies". Over 200 people showed up, and we advertised the next one "The Grinch" (for December). About 40 people. January saw "Rudy" (in honor of the Superbowl). About 20 people. Then we did "The Princess Bride". About 20 people again. Concessions take could not cover rental and shipping, so we axed the idea. We weren't trying to make a huge profit off of the films, we were just trying to offer something unique, and hopefully cover the costs of getting the films. It was a real pity, too, as the people that were coming really enjoyed the events. We did some giveaways, everyone got a real ticket, and we received compliments from all that attended.
We also did a one week run of "Willy Wonka and the Chocolate Factory" 3 years ago. Advertised it, did some cool giveaways via raffles at each show, etc. The 15 people that showed up all week enjoyed it, but it was a failure from a business standpoint.
We are trying to put something together for Halloween involving classic horror movies, but are leary of investing too much time or money into it due to the failures of similar endeavors in the past.
I can't imagine trying to run classic films on a regular basis and counting on them to keep the business afloat. They're nice to try once and a while, and you may attract some customers that wouldn't normally come to your theater, but it can't be the backbone to your business, imho.