We're remodeling and we're having some shelves built next to the fireplace and we'll need a display. The shelves are around 45 inches wide by 12 inches deep. I'm not sure just how big we can go with those dimensions, it'll be the width that is the limiting factor.
There will be an arm that holds the display in and can be swung out for viewing. I've been away from these forums for a while so I haven't kept up with the latest technologies. It will be in a room with indirect sunlight from a window and french doors so assume an LCD would be preferable to Plasma which we use for our "main" movie viewing.