Maybe paint the wall with a accent color to make the shelves pop off the wall. The art work might even look great with a complementary background color. A soft rust color would do wonders! I would move the painting up about 4 inches to center the space also.

I agree with centering the couch. Maybe stagger the shelves at an angle across the accent wall behind the couch? I would love to be able to see the new couch!

Art is from Pier 1. They have several large pieces that you might like and would work in the space.