Try using light and bright bedding. Pull the sheets down on the bed -- makes it more inviting. White sheets are great to use because they're bright, don't fade and matches with everything. Beach themes and colors are also a great way to liven up a room at this time of year.
King bedding, $99.99 from Dwell
King sheet set, $99.99 from Bed, Bath & Beyond
Nautica king bedding, $149.99 from Bed, Bath and Beyond
Lamp shade, $88