I'd go for a white, transitional mantel for the FP. Are you keeping the white furniture? I'd go white on the mantel. Wait, scratch that! You have the black slate hearth. How about a "rustic" wood simple mantel.

i would not put mantel at all. instead i would add shelves on both sides

It's a very rustic fireplace so I'd go with a large, medium to dark rough sawn beam for the mantle.

And you should think about putting the TV on a credenza at eye level when seated or you and your family could end up with chronic head and neck pain due to the development of myofascial trigger points from having your head tilted back in an unnatural position.

Thanks. We actually just mounted the TV on the fireplace otherwise it was tucked in the back left corner and really hampered our seating arrangement. The slate hearth can go too...would love recommendations on what I can replace that with. I want to keep an open airy feel. I have a dark wood topped table hiding behind the couch on the right, which can move, but directly in back of that couch is our dining room with other wood. The couches will be grainsack material from pottery barn and colors are neutral with spa blue. White coffee table is too big for space so will move, but not sure yet what will replace it. See more attached. Sorry for the dark night photos :(

Also, could do something like this, but what about side walls then?