Hi Rugby Pumps,
You are so lucky to have such a big space! You are correct! you need the right area carpet to pull the whole thing together. I love the way you handled the TV wall.

Now you need to do the following:
Establish your Budget: Carpets vary in price according to their content of fiber, both thickness and the type. Wool carpets in the 8 x 10 sizes will run you between $4000 and $10000 dollars- each one made by hand. Sisal carpet could cost as low as $200. Big box stores say $500 to $1200. But in my shopping I have found some incredible sources for rugs.

You will need to put an underlay under it so it will not slip - the carpet company will supply that. Its around $250

Do you have animals? I ask that because a client of my let her cats destroy her oriental and it needs to be repaired now which will cost around $500 to cut and re bind the edges
Area carpets are sometimes an investment. for a home owner, it is also considered art on the floor.

Determine what size: By counting the tiles it looks l like an 8 x 10 or 8 x 12 will work.

If you are on a budget I will suggest Flor:
You can do some really cool and funky things with Flor. Its a carpet tile that you design with your own sizes and patterns and colors. Its very inexpensive relative to wool but its only nylon - made from recycled carpet. You can order online with the help of their designers.

I will add some images of some beautiful and inexpensive carpets. For a bit more info on this you can go to my facebook page at www.facebook.com/shelleyscalesdesignassoc

Good luck!