I love brown sofas. Keep the walls lighter, anchor the space with a light-color textural rug, and limit other dark browns to an accent chair or a picture frame. Bring in midtones such as hot pink, red, and teal.
Faux Built-In Bookshelves - flank a doorway with identical bookcases that reach almost to the ceiling and install moldings around the tops of the shelves. As a style bonus, paint the bookcase before installation, or line the backs with pretty paper.