Personally I prefer to use a mottled or tone on tone (think Moda Marbles/Michael Miller Crystal/etc. for the background in blocks. Solid solids tend to read a bit "flat" for my taste. <G>
But it is your quilt, you can use whatever you like for the background.
If you can get a few different backgrounds that would be options, check several different of your scrappy fabrics on each background. Take a digital picture of each. Check it on your computer screen. Also check a bit later to see if you have changed your mind.
Remember that you will be using quite a bit of background, you don't want to get bored by it. <G>
Pati, in Phx