I was going to suggest a deep blue grey, similar to the top right picture kah416 posted. It would be a beautiful contrast to white and timber, and would work with many different accent colours from pink to orange to green.

With regards to furniture placement, your trickiest element will be the off-centre fireplace. Do you have a spot for the TV in mind yet? I would definately suggest a larger statement piece of furniture (or a buffet/sideboard with a large piece of art above it) next to the fireplace to balance the height of the fireplace in the room. Did you have any furniture in mind yet?

i think this will look great xx

a light grey or blue grey will look nice on the right wall. the other wall i would leave them white

I would put a color like or on the firplace wall. Here is one space with Kendall Charcoal:

I would mount the TV with a low cradenza on the wall.

The wall opposite the windows I would paint or

I would place a large sofa on that wall with a great big piece of art over it and an end table and lamps on either side. This is a sofa with clean lines: A rectangle coffee table in front.

Next to the sofa facing the TV I would put a chair. One the window wall I would have one more chair and a end table with a floor lamp.

I would do a rug with lots of color.

We were planning on putting some sort of storage/ media unit on the wall next to the fireplace to set the TV in. I like the color options in all of the post. We don't have furniture yet but we were thinking of brown leather. Would this go?

Brown leather could work but I would choose a warm, sofa leather rather than a very dark, modern look. Try something that looks a little worn or is a classic style like a Chesterfield.

Please keep us posted. I would love to know how you end up arranging your furniture.