It's tempting to go all white beach house but your setting looks more northern and woodsy. Painting the beams may be a good idea and leave the stone fireplace with as less ornate or no mantel. Choose colors to play up the stone to add warmth and cohesiveness to your design. Actually the colors in the attached pic may work for your home .

Your fireplace looks as though there is a section added on to create a wall to the support beam. It looks a liitle off balance and if you could remove that section it would enhance the beauty of the fireplace. The light floors are very nice.

Agree with paint ceiling a creamy white, leave beams darker (although too bad if they're painted), leave floor until you see the paint -- it's pretty nice light, and you might repent darkening it. Would cool the tone of the paint a bit, but otherwise seems ok. Paint brass on fireplace black (with paint made for that purpose) and replace inappropriate mantel with a rustic beam style. Minimize fussy zone of windows, and wood trim at top of walls. Otherwise, beautiful space!!

Congratulations - what an amazing location! I like the color palette suggested by Martha for the ceiling - this brightens the space but keeps some of the rustic feel. Also replacing the mantel with a rustic reclaimed piece of lumber in a driftwood color will tie in with the color palette. Refinishing the brass fireplace surround to a matte black will update the look, plus consider gas log inserts which simplifies the entire process of making a fire. It's a beautiful space.

I would paint the ceiling between the beams white and leave the beams as for the fireplace remove that weird mantel and replace with a full lengty reclaimed wood one if you want to this is also a perfect fireplace for T.V. above if you need to. I am thinking the add on on the fireplace was to create a join for the post if possible I would try to cut the stone out so that just the actual fireplace remains and then beef up the post since it seems to be a support. I agree with the fireplace metal in black too.

https://www.houzz.com/photos/gathering-place-traditional-family-room-birmingham-phvw-vp~214155

I agree with carolyngarland that you'll need two seating areas in the large room. Swivel chairs in the area of the big windows, around a large ottoman or round coffee table, will allow the conversation to be centered around the coffee table or toward the dining, kitchen, or other seating area. Swivel chairs may also be turned to take advantage if the view.

Like the existing stone as is. Just 86 the mantle and the brass fire doors for starters.

Replace with minimal glass doors like these.

There's no way I would paint gorgeous timbers like that - look into having them soda blasted back to raw wood. But the same goes for the window trim! To do any treatment to the beams and not unify the equally overpowering dark trim around the windows makes no sense. They must be part of the equation here - to leave them as is will leave the space looking unfinished. And to paint a T&G ceiling in fantastic condition is a complete blasphemy IMO. Refinish the floors to unify all the wood tones and you will end up with an amazing space. And switch out the brass for an efficient fireplace insert that will actually heat the space as opposed what is there now. Best of luck.

This is the way the Sherwin Williams computer sees the fireplace photo. Except for the golden tones caught from the bit of ceiling, I think you could use any of these colors in your room. I think my personal preference would be the Poised Taupe (in the greige family) or Network Gray for the walls, then paint the beams up top with the Grays Harbor (which looks like your vertical support beam) or other color from the right side column. Reserved White, or an even brighter one for the wood between the beams.