Three, differently-colored, basically plain walls.
I mean like .... a big wall, where you can see the edge of the bookshelf to the side and there's a lamp in the way ....... not, like, one square foot with nothing but wall.

I have kind of a thing for that. Who knows.

Failing the above, views through windows.
Right now. Dark out, with all your lights on inside, that's okay by me.