This, of course, is a personal preference and you can use any background color or image you like. There are a couple guidelines we recommend though. If you want the optimal desktop background, then a neutral gray is recommended. Our eyes can be influenced very easily by vibrant color: a neutral gray is the least distracting.
If you choose to use a picture or vibrant color as a desktop background, then make sure your program or application covers the entire screen so the background does not show. If you are using a secondary display with a picture or vibrant background, then make sure to cover it with either the secondary application window or simply turn it off. A secondary display with a vibrant color can be affect your color perception on your primary.
This illustration demonstrates the way the human eye perceive differently just because the environment and light characteristics changed.
Have you noticed that many editors offer the ability to change the background color? This is to help your color perception. You will notice that programs or applications have a very neutral color pallet for this reason.
Of course, it is always recommended to control the lighting in your environment. Best practices are the room lighting should be fairly subdued. A good rule of thumb is your monitor should be the brightest light source in your room. Direct light sources should be avoided and desk lamps should be turned off during calibration and while performing color critical tasks.
We found on panoptikum.net a very good example of how we perceive sometimes images wrong. A and B are exactly the same colors but we perceive B darker than A.