Artwork falls under that category we decorators and designers call accessories. What is ironic about that is that many times the artwork is the inspiration for the design aesthetic. A single small canvas painting or print or piece of sculpture can influence the color scheme and simplicity or complexity of what else is chosen for the space.
Consider a carved wood figurine found while vacationing in Indonesia, purchased and carefully transported to it's new owner's home because of the "feeling" the new owner got when he or she found the piece and couldn't walk away without it. Translate that "feeling" into some specific emotional reactions such as happy, delighted, intrigued, relaxed. We have now identified exactly the emotions we designers will want to incite for the room's owners (and hopefully, also for it's visitors) and have a "jumping off point" from which to start and can identify appropriate furniture and textiles.
Now imagine a very large, graphic, abstract and brightly colored painting, and how different the space around a piece like that should feel: exciting, fresh, avant-garde, untraditional, etc.