We've all seen them, that dark dungeon of a basement that seems almost moist to the touch and reflects less light then a black whole. A forgotten about room that that serves no other purpose then hiding that one strange child from company. A windowless room.
Windowless rooms tend to find themselves in basements or bathrooms. They leave out any option for natural lighting, and when not considered properly, regular light fixtures can tend to cast big or unattractive shadows leaving the space feeling glum. If not chosen correctly for the space, colors may come out over saturated. Although you may need to get a bit more creative with these spaces, there is no reason why you can't make it feel as open and cozy as any other room in your home.
Lighting is going to be one of the most important things to consider to help brighten up the space. Consider layering the lights, don't just rely on your ceiling fixtures in the middle of the room. Do find a nice center fixture that sheds light across the entire room, but also make sure to get some lamps and other light sources. Standing lamps work great for corners, and desk or table lamps work well to help add brightness to more focused on areas. Consider at least 3-4 light sources in the room. A dimmer is almost essential to help soften lights and make the space feel more inviting.
Walls + Colors
Make sure to chose a lighter paint color in these areas to help reflect light across the room, you do not want to chose darker colors that absorbs. Look for a wall that doesn't contain any breaks from windows or doors, this is a great opportunity to feature some quality wallpaper to really help the room pop. Make sure to pair the wall and furniture colors together well, try not to overdue the colors, stick to 2-3 pallets.
You may want to spend more time considering the flooring you chose in this space. You'll find that in a windowless room the flooring will get much more attention. Would a rich hardwood help bring out the comfort? Maybe some classy linoleum will keep things looking sharp. This is also a great time to throw in a nice area rug to help tie things together.
Don't forget the accessories. Hanging wall mirrors work great to help reflect more light and will make the room seem more open. You've also got tons of wall space, so don't be shy on hanging some larger artworks or prints. Another great way to liven the space up is to add some lush or green house plants to clean the air and freshen things up, but make sure you get the right plants and know how to maintain them properly.