It all depends on where you hang your print. You don't want it to look too small, but you don't want it to overwhelm your room. These pictures are based on a couch measuring eight feet wide, and plenty of blank wall space. Every space is different, but use this a guide for sizing your print.
You might find it helpful to cut out a piece of cardboard to the size of the print you're considering. Hold it up to your wall and make sure it doesn't feel too small, or dominate the space too much.