Shiplap
Shiplap is a great way to add a bit of subtle, timeless character to a wall in any room. Installing it vertically, as opposed to horizontally, also helps make the room feel taller/larger as the vertical lines tend to draw the eye upward.
Shiplap comes in a number of widths that can be used to achieve different aesthetics. It can also be used in lengths that span the entire wall or shorter pieces can be used and offset to resemble a brick pattern.