Wow - you have a large room, but it is long and narrow. If you put the TV over the fireplace where will the chairs be relative to the screen? Will the screen be too high making you feel like you are in the front row of the theater?

http://lifehacker.com/5993910/why-mounting-your-tv-above-the-fireplace-is-never-a-good-idea

I added more photos to help visualize.
We ordered an L shaped sectional, 132" couch will sit where the TV is currently sitting against that large window. Then an 86" piece will sit where the current couch is sitting. We created an entryway for our front door with the back of our couch and will eventually place a table under the picture on the wall to get it more of an entryway feel.

If this is a non working FP and just for show, then mount it. It is never a good viewing experience like one on the wall or the floor. Your room is not wide, but look at every option for furniture arrangements. Since I have no idea of the furniture in the room, it is difficult to recommend a good floor plan.

I measured and it is going to be about 6.5 feet from the ground. We have 8 ft. walls.

Some inspiration , good luck!

Really hiding the cords, as in these photos, usually means getting a lot of the stuff inside the wall -- that is, running a cable jack and an electrical outlet so that they are behind where you intend to hang the TV, and ideally also a conduit for the cables that need to connect to other components (over to a bookcase or shelf). That can be tricky on a fireplace wall. Otherwise, you're going to need a wall-colored cord wrapper to convey all the cables down, along the mantel, and over to wherever you're going to plug them in. (I've also heard of wireless cable, or you could maybe get a smart TV that can get signals from a bluetooth box or the like, but you asked about design, not technology...)

KiOS,llakkslelelwlaps

To test whether you'll be comfortable with the height of the TV (because many people are not comfortable gazing upwards for long periods), stick a piece of paper on the wall where the CENTER of the TV screen will be, then sit in the same spot you'll be sitting to watch TV. If it feels comfortable after 10 minutes of looking at the paper, then the height is probably ok for you. I think you'll find this article very helpful: http://www.cnet.com/news/how-high-should-i-put-my-tv-morrisons-mailbag/

My family room is 12x18 and we mounted out tv over the fireplace. Best decision we ever made. And we use our fireplace in the winter. Heat is a non issue. If you place the tv as the same height as the fireplace, but put it next to the fireplace, it's just as much of a heat issue.

I can't wait to show my hubby all of this great insight. Thank you all!!!