The rule of thumb that I use is that the bottom edge of the display (the actual screen, not the surrounding frame) is at the eye-level of your primary viewing position. So, if you will primarily be viewing from a set of recliners, sit in them (upright ... don't recline) and have someone measure to the height of your eyes. Make that height the bottom of the display image ... a few inches up or down won't be noticeable, though.

Definitely a corner FP. Most houseplans have them in the middle of a wall and it will restrict you in furniture and TV placement. Unless it's a short wall with built-in's on either side. A corner FP will free up all the walls for furniture, TV and windows. I love our FP in the corner. We have a TV on one wall along with a window, and the other wall has plenty of wall space along with two large windows. This way we can enjoy the view (we're in the country), TV and FP at the same time.

I would raise the drapery rods so that they are about halfway between the top of the window and the crown moulding. You have the transoms and taller doorways, and the windows end up feeling kind of squatty with the drapes hung right at the top of the frame. You can use clip rings if needed for more length. I would turn the rug the other way, parallel to the couch - it looks too small the way it is running now, compared to the width of the couch. Add a floor lamp to the right end of the sofa by the wall, and slide the couch a bit more to the right - it doesn't have to be centered in front of the window, and will give the room the feeling of more walking space move over to the right a bit. Take the tall cabinet and put it on the left side of the console cabinet, to create the feeling of a larger entertainment unit. Take the big plant off the top and add a nice plate on a plate stand up there, perhaps a pair of candlesticks or a smaller ivy plant. Take the single chair and put that on the right side of the cabinet, as extra seating. Add a lamp on the right end of the console by the chair. Something in red, either the lamp or the shade, would be nice to bring some red to that side of the room. The height of the lamp will balance the height of the taller cabinet on the other end, and also provide some warm lighting for the person seated in that chair. Try bringing in the two wing chairs and putting them at a soft right angle to one another down at the right side of the fireplace. A round table and lamp between them would be a good addition. A fabric ottoman that could act as a coffee table and extra seating would be nice in front of the couch. Something narrow and simple in design, or even a pair of the square ottomans in a bright red or rich moss green would work. The mirror is great, but too small. Try to find a large piece of art, or even a pair of framed pieces. The mirror will only really reflect the tv, so not a bit bonus to have a mirror up there. Add some taller candles in holders, perhaps the vase of grasses currently on the hearth. Once you bring the lamps in by the couch and wing chairs, you likely won't need a lot of art on the walls on either side of the fireplace, but wait and see for sure. You have a great start in the space - just need a few things to pull it together.

Is the 14'8" the measurement from the window wall tom the kitchen wall? And do you need to maintain a "hall" that runs down that kitchen wall to the master bedroom? If so, it seems like the wall where the TV is now is the logical place for it to stay. The room would lend itself to a sectional, if such a solution would work for you. It would create a natural path around itself and keep the TV area more intimate -- no need to walk between the TV and the seating when crossing through the room. I had a LR that was 12' wide (with an 18" fireplace hearth sticking into the middle of it) and 20' long. The TV was on one of the short walls. It was hard to find a seating arrangement that didn't look something like a mini van, especially if I was bent on having a full size sofa and my hubby was bent on sitting in His Chair and not on the sofa with me. It was either have a chair slightly in front of the sofa, or have either the sofa or the chair(s) not really facing the TV. You could do a sofa perpendicular to the front wall (walk in the front door and the back of the sofa is on your left) and then two swivel club chairs facing the front wall (backs to the kitchen). That way it would look "nice" when empty, but the chairs could swivel for TV viewing.