I would add some fabric panels on the window, art work, a chest of drawers. I would pull the bed away from the wall if possible or move it to another wall and add two nightstands.....without a picture of the whole room it's hard to tell how much wall space there is. I would also use lighter bedding for an airier feel..the current bedding seems too dark in relation to the wall color. Then lamps and other accessories of course.

http://www.ikea.com/us/en/catalog/categories/departments/bedroom/tools/cosl/roomset//

I'd go to Ikea and get a headboard/frame, nightstands, dresser, lamps, art, mirror, curtains, and maybe bedding if you want something new and not so dark. Browse through the bedrooms in the link and see if anything appeals to you.

Or go to www.apartmenttherapy.com

Lots of great advice, including DIY headboards.