First thing to do is make sure you have the optimal efficient layout. Even if you think you do, I'd strongly recommend posting it here. The folks on here saved me from a huge mistake, had I gone with the design of the "highly recommended genius architect" that I'd hired to design my kitchen.

I understand you love shiplap, but I feel like what the above commenter said is very true in the case of your fireplace surround and mantel. It is very traditional looking and probably wouldn't look good with a shiplap accent wall around it. If you ever decide to change out the surround, then that would be a great wall to accent. Did you look on Pinterest type sites to see what types of areas look best with shiplap accents? That's really helpful to get an idea what looks good.

I don't really think shiplap would give you much bang for the buck in this space. If it were mine, I'd focus on revamping the artwork on the walls, replacing the mirrors with something that holds personal meaning, and maybe doing something more dramatic with artwork where you have the map. Something that reminds you of favorite travels or places, perhaps? Enlarged personal photos or big original canvas paintings?

Our living room needs to be repainted, but has vaulted ceilings and connects to the foyer and hall (the staircase is painted the same color too). I'm thinking SW Pure White like other areas of the house, but I'm not sure. I also need to replace the old, dirty carpet on the stairs and floor, but I have no idea what to put in. We do not want to raise the floor and continue the hardwood, so I am looking for different suggestions.