In the photo above, the space is small but doesn't feel cramped, even with all of the furnishings. A large mirror reflects light, and furniture has narrow legs allowing you to see through to the walls or floor of the room, or furniture is glass or mirrored. You can even see through the lamp on the side table!.
Scale: Don't get the mammoth sectional for your cozy living room. Get a settee or a smaller sofa with narrow arms and petite legs that take up less visual and physical space.
Reflect: Don't neglect or waste the natural light in the room. Place a beautiful mirror on the opposite wall of your light source, and/or get mirrored or metallic furniture and decor with reflective properties.
Through: Find furnishings and/or decor you can literally see through. This means furnishings with narrow legs, backless bookcases, and glass or lucite tables.
2 images above via Little Green Notebook
Lucite is great for small spaces via Domino
Below are examples of pieces that would help keep a small room looking open and inviting:
Get it here.
Get it here.