1) Go dark
I don't believe that small rooms always need to be painted in light colours. It all depends on the room’s use. A bedroom might warrant a warmer choice of colour, whereas a bathroom might benefit from cooler shades. If it's cosiness you’re after, a very dark blue can be extremely effective.
Which paints? Try Arctic Night
2) Create the illusion of height
Paint your wall colour up to about 10cm below the ceiling, or up to the bottom of the cornice if you have one, then paint everything above this white. The extra band of white will visually stretch the ceiling height, making the room appear taller. Deep teal tone looks smart against a crisp white.
Which paints? Try Blue Grass
3) Broaden your corridors
I’m not a big fan of feature walls but one situation I would recommend them for is if you have a very long, narrow corridor. A dark colour at either end helps to draw the eye and make the space appear less stretched. Try a rich red for a dramatic look.
Which paints? Try Wildflower