From early concept art to marketing illustrations to final in-game assets, art takes an important role in game design. It can be a daunting task figuring out what kind of art your game needs, how to hire and direct artists, and finally implementing all of that in a way that works.
Depending on what stage your game’s development is currently at, some sections of this article may or may not be applicable to you, however it covers a cursory look at the process for sourcing and implementing art for games.