Here is the main living space of a basement apartment I designed that has no windows. I had to get creative for my client that loves nature and the outdoors. I started with this huge photo stretch canvas of a tree and sourced a modern beautiful rug to go on top of the new wood-look flooring. All the furniture is small scale and upholstered in the same fabric to keep the space looking and feeling as large as possible. And almost every piece is multifunctional. The couch is a hide-a-bed for frequent company. The ottoman is on wheels and can be a bench for extra seating, a soft place for stretching out feet, and the trays stored underneath can come up and work as a table or a place to put drinks. Even the sofa table is a place for critical storage.
The neutral wall color is the same on the walls and the ceiling. The dark green accent color is pulled from the tree photo canvas.