Some things to consider:
1. 12-15 feet are maximum distances from which you would want to view TV, or have conversation. If you have a furniture arrangement where you have distances larger than that- go back to the drawing board.
2. Consider two separate areas. One could be a desk, with the second a sitting area, or perhaps two sitting areas. You could also add a foosball table, or similar piece on one end. Doing a little math, a sofa might be about 9 feet, and even very deep chairs are only 4 feet, so a sitting area with a sofa and two chairs is only 19 feet in length, and even that is beyond the 15 foot max that I would recommend for the two people in the chairs to have a conversation. Translation: Don't try to stretch out one seating arrangement in this space. Consider your needs and create two areas. You could also add a small game table, or a bar on one end. (photo from Freshhome.com)
Here are some ideas:
Sofa with chaise, and a chair, with a bar at one end. (pretend that kitchen is a bar)
To seat a few more- consider a settee paired with a sofa. Add a small table with chairs. Draw it all out on graph paper. Make sure you give yourself traffic paths.
(from danielle oakey interiors)
3. Area rugs help to separate areas. When you try to make one area into two, they help define the space. Hanging lights also do the same thing. If you add a table, add a hanging light over it.