http://www.flickr.com/photos/60013369@N03/5480119776/I played with your photo a bit. Hope you don't mind. You really just need more lighting. If you have any natural light bulbs I would pull them over to either side of your fireplace. I personally like workign with natural light (so maybe try and find a setup closer to a window?)
You can lighten up the shadows like i did with your picture by selecting the background and overlaying it with the lightest colour of the wall (i filtered it to be about 60% opaque so some shadow still showed) then I filled in some "Faux" shadows to match it all up. Then i just brightened the original image layer by 30% to make the white pop more.
I did it quickly but you can improve it with these methods. I would however try and get the best lighting as it makes the editing much easier.