Paint and Decor Color Advice?

We want to paint our room gray and white. It has one window, little lighting (hence the color choice), an open shelf which is beach in color and a small table in the same color. I don't want to change the color of these two pieces.

So which wall should I paint gray and which white? What can I put as decor so that it doesn't turn out a bore? Any ideas on the colors of the decor?

By tery from Tanzania