We've used those lockers in the past (about 5 years ago), and I don't think they are big enough for a rolling carry-on. The ice chests I've seen put in them are the sort that would hold a 12 pack of soda - not much larger. That picnic area used to be much easier to access than it is now. I believe the last time we tried to use it, the entrance to it had been moved to the outside of the security check area (used to be by the entrance to the bathrooms by the guest services window). May have changed in the past year, as we haven't tried to use it since Fall 2006.