Why would you install shiplap there? That space is mostly TV.

And vertical shiplap? No no no no. Only on HGTV.

If you have to do anything, match the doors.

Horizontal Shiplap

https://www.youtube.com/results?search_query=shiplap

Look at a few YouTube videos before you start your project.

Horizontal if you must but I see no reason for shiplap anywhere BTW what you think is shiplap is just boards put on a wall no one in their right mind would put actual shiplalp on a wall anywhere

I get what you are trying to achieve. A little pop in your room. I am assuming over the TV you have open space. Another solution that would not be permanent and can peel off when you get tired is plan wallpaper. No one knows the different and they actually sell it at Target and Walmart. I did a little space in an area (see photo). It is just wallpaper and no one knows the difference. When all this shiplap goes to the wayside, I can just take it off.