Depends on the wall and the room. For instance, bedroom:

Dining room, I would have it on four walls"

It would be for a living room

Do you think it should go all around the room instead of o e wall?

I mean instead of one wall?

I would let the fireplace be the focal point. Adding a wall treatment to a fireplace and TV wall sounds like too much.

When I see these rooms with one board and batten wall I wonder if it was done as an easy fix for some kind of wall problem. Because I have considered it as an easy fix for a wall problem :-)

Looks like battens and panels to me, or architectural paneling.

It really depends…but it sounds like your wall with both a fireplace and the tv is already the wall that gets the focus, both because your furniture is most likely arranged around watching tv and because fireplaces are almost always features in a room. Adding even more visual weight to that one wall with added molding could make the other 3 walls feel pretty bare (unless you have out of the ordinary windows or really large pieces of furniture or amazing art on the other 3 walls). In your case I’d go all walls or none, but actually I’d go all walls because molding, done well, is always a good choice.

If your intent is to make one wall of a room appear to have originally been an exterior wall, board & batten will work but I don't know why you would want to do that.

For better assistance provide some photos, inside and outside.