Having a windowless room in your home doesn't have to mean it's gloomy. With the right paint, furniture, accessories, and lighting design, you'll wonder what all the window fuss was about in the first place. Additionally, if an adjoining room gets natural light and renovations are in your budget, hire a professional contractor to widen your doorway and let the sunshine in.
Paint the room bright, sunny shades found in nature to mimic the outdoors, like yellow, light green or very pale blue. Use high gloss paint so that it reflects and amplifies light. To emphasize height in the room, paint vertical stripes; to emphasize width, paint horizontal stripes. Choose a color for the stripes that is slightly lighter than the base coat for a spacious, airy effect.
Install various light sources to imitate the way the sun moves and changes the quality of light throughout the day. Place wall sconces high up, toward the ceiling; other suggestions include tall floor lamps, multiple overhead lights and table lamps. Replace dim bulbs with the highest wattage bulbs you can find to make the room as bright as possible.
Hang mirrors to reflect space and amplify light. Place mirrors directly across from light sources, either at eye level or within the top half of the room, to imitate a window. Hang seasonal, nature based art across from mirrors, to give the impression of looking at what's going on outside. Rotate your art to reflect the dominant color of each season; suggestions include brown in autumn, white or red in winter, coral in spring and green in summer. If it's in your budget, install a floor-to-ceiling wall mirror to double the appearance of light and space in the room.
Install a focal point that imitates a window. Group panels of mirrors together in a square formation to imitate window panes or hang a small, painted trellis on your wall. Paint your "picture window" wall a lighter shade than the other four walls, to create the impression that you're looking outside. You can hang curtains around your focal point to complete the effect.
Brighten the room by keeping the floor as light as possible. Install light-colored wall to wall carpeting and/or put down light colored area rugs.