You can try to lighten the room up by pairing the dark walls with lighter furnishings and accessories, such as curtains and wall art. This creates contrast in the space and helps the room feel lighter.
You could also try adding more lighting to the room—a few lamps can make a huge difference.
Another option would be applying a paint treatment such as rag rolling in a lighter color over the dark brown.
Explore a variety of styles at kitchenbathideas.com. Overlaying another color would add depth to the walls and also help to lighten the walls while still keeping the rich brown color.