To make a room appear larger

Choose colours from the cool end of the colour wheel.
Paint all surfaces the same colour.
Keep flooring dark and walls light , the floor space will appear to expand.
A low ceiling will appear higher if painted a lighter shade than the walls or put some mouldings up and paint them a darker shade than the ceiling.
Use the deepest tone of colour near to the floor and the lightest shade on the ceiling. This will give the illusion of space. Try it the other way around to see how a room can be made to look smaller.
Large pieces of furniture will appear smaller if they are the same colour as the walls.
A small room doesn't have to be painted in light colours. Emphasise its cosiness by painting it a midnight blue or deep red.