A few pics I got on May 3 of CLE Concourse D getting more action than it ever had from mainline metal. Plenty of ERJ-145s and 737s there. There were United Express 70-75 seaters over on the other side of the airport as well.
A press release from 1999 about the opening of D said that the facility could handle mainline craft, but it never did and it seems that it only could if the next gate were left open or something--D only ever handled Express flights really). Seeing all these mainline planes parked around D was really freaky, although none of them were loading or connected to jet bridges.