Spending a little time staging an unfinished basement can really give the lower level of your house a little more umph. What I love about these examples is that they have the visual impact a lot of buyers need to see that the basement is large enough to be finished and furnished one day.
Tip 1 - clean the windows, the basement windows easily collect grime, cleaning them up shows that there is actually natural light even down in the basement.
Tip 2 - Create a seating vingette, you probably have some furniture stored down there anyway, set it up like a little sitting area with an area carpet, pillows and floor lamps
Tip 3 - consider painting the ceiling white, this can take a basement from drab and dismal to bright and loft-like
Tip 4 - paint the concrete floors...it just looks fresher
Tip 5 - create a play area