I had my first open studio and the thrill was incredible. My studio mates and I ordered panels and painted them white. We cleaned up the studios and hung up our art work in the large common area of our space. The thrill was amazing. There is nothing like seeing your art work on white walls. Why?
When you are looking at a painting the background becomes part of the whole. As in gestalt theory, developed by German psychologist in the 1920’s, states that we perceive visually the totally of the background and the image as a whole.  It becomes a unified field that the brain tries to place in categories.  In other words the background and the painting becomes one. If your painting is in an easel then the background is part of the total filed.  You move your painting around and it changes. When painting plein air it is not a problem because the painting and the background are unified.
When we alienate the painting on a white wall the gestalt of the painting is what is in the canvas itself. It is the quality of the line, the brush strokes, the use of colors, the structure of the painting (could be composition), etc. becomes the surface that is perceived and appreciated. They are the elements that the artist uses to convey a message and complete the gestalt of the image. It is only then that the message is complete.