It just makes the room darker. You have a few inexpensive options to make your basement look better. You can cover the walls with light colored pictures or posters. Painting is the most effective, and can look very nice. Clean, dust, sweep, and paint the cement floor is you have to.
Nothing dates a home more than a cluttered, grease splattered, and water stained mess of a garage.
This will probably be your biggest challenge, but don't neglect it. With most people, a few trips to the dump would probably be in order. There are many factors that go into the sale of your home. This advice is the result of my positive experiences.