I looked at your shop (VERY nice!!) and noticed that you don't have lighter backgrounds on all of your items - that was going to be my next question - should I change ALL my pics or just some of them?
To answer your question - I white-washed an old wooden board and put a white poster board behind it. Not sure why some are whiter and some are blue - they were all taken within a 30 minute period. Have to figure that out.