Your office is that part of the home where serious stuffs are discussed, planned and executed, so for your office wall art, you might not want to go all aesthetic and playful, and at the same time avoid being too serious. You want to strike a balance between both themes.
With this, you can use beautiful and bold Canvas art designs, printed art works, posters relating to the field of work, a gallery wall to capture work moments, or pictures of the people that mean so much to the office occupant. For poster options, you could try, the world map, pictures of standard boardroom and so many others.
Another thing you could use in your wall art for offices is the choice of color for the wall.
Different colors can be used to depict different moods, so you could also try combining some colors or using color patterns to achieve a nice looking, functional office space.