Painting a room white or a light color can brighten up a space and help the room look bigger. Nothing creates a better illusion of space than the color white. Make sure when choosing white that you also use other colors so that your space does not look dull. You can play with a few colors and patterns that look bright and add interest without darkening your room.
By painting your ceiling white it can open up your space. Here is a great example of a room that has a rather dark and deep color scheme. With the trim and the ceiling painted white the space looks brighter.
Using mirrors is a great idea because it is reflective and creates the illusion of more space. You can increase the appearance of the size of the space by adding wall mirrors. They are perfect element to add because they reflect light and color. A repeated pattern of mirrors hung on a wall can easily add as a decorative element as well as make the room look much bigger.
Using the minimalist approach opens up a space. Placing to many pieces of furniture in a small place can overwhelm the room. Also remember to limit the number of accessories to avoid a cluttered feeling.