You know it when you see it: dinky furniture in a large room or an 11-by-14-inch family photo mounted over a fireplace with a two-story ceiling. And adding more items doesn't seem to help.
Solution: Try to choose fewer, more massive things. Luckily, gigantic armoires and sectional sofas aren't difficult to find; they're everywhere. Also, large pieces work equally well in smaller rooms and give the illusion of space-just don't use too many of them.