Lighten those walls, remove existing drapes and put some simple rods higher up on the wall (almost to the crown), and wider than the window. Add full length panels to the floor. Consider a subtle pattern or solid, light like the walls. Use matte / linen, Possibly a striped dhurrie rug and weathered wood narrow table. Chairs on the back wall and use a bench on the long side by the door. Something different for host and hostess chairs - maybe slipcovered. Casual / rustic chandelier.