If you do not have an appropriate wall, you could make use of a ceiling TV bracket. These brackets are also of use in business premises with large open spaces as they can be positioned in the middle of the room.
The majority of ceiling brackets will tilt downwards to allow people to see the screen better as they will be positioned at a height. Many ceiling brackets also rotate by up to 360 degrees, allowing you to put the TV in the middle of the room and see it from anywhere around.
Some of these brackets have long arms in case your room has very high ceilings.