About a year ago, I was asked to put together a quilt for a fund rasier in honor of a woman who had died from cancer. The fabric had all been picked out by her before she had passed away. When it came to the backing, I didn't have enough of any one fabric, and I wanted to use just "her" fabric. I did a sort of crazy quilt using large random pieces. It came out beautiful. I quilted it on my home machine, but because it was so random, I didn't have to worry about lining up with anything.
Since then, I have tried this several times. Last time, I used large rectangles, and placed them diagonally. Again, it was beautiful and well received.

Most quilt shops & the internet have 108" backing fabrics for quitls, it is better than buying yards of fabric & sewing it together for backing, they have really pretty colors also.

In the late 1980s a couple of friends of mine wrote Back Art - The Flip Side (Danita Rafalovich & Katherine Pellman). I started piecing backs and will never put just one solid fabric on the back of a quilt again. Here is a link that shows some interesting flip sides http://www.popularpatchwork.com/news/article.asp?a=6922

I do what Bonnie Hunter suggests, I make the backing from 10 inch finished squares. It's easy to calculate how many you need and you can get 4 squares from a width. I try to use fabrics that relate to the front of the quilt, any leftover fabric or extra blocks, but I also try to use up some of those "what was I thinking" fabrics. A bonus is that after you've trimmed up the layered sandwich, you should have strips that are perfect for a pieced binding.

I really, really like this idea. I think that if you pick the colors smartly, it could be really attractive. I'm going to try this on my next quilt.

No one has mentioned this...when hand quilting if the seam in the pieced back is directly beneath a seam in the top, it's almost impossible to make nice quilting stitches through all those layers of fabric. I try to avoid piecing my backs for this very reason. Quite often they line up and then I have a problem!!!!

The first quilt I made started out to be 9 patch for curtains for my laundry. Well, needless to say it kind of grew. I had lots of scrap pieces that I had gotten from deceased relatives. The quilt ended up being two sided. One side is winter (in blues and rust) and the other side being summer (in yellows and rust). The rust were the shashes between blocks. Only problem I had was when I got it back from the quilter, it was really heavy. Because of all the seams.
The two sides design didn't line up but the quilting was random so it didn't matter.
Rita

I still quilt by hand as can not get the hang of MQ. When I do a large quilt I find for me it is daunting to quilt the whole thing as one piece, so I do a section at a time then sew them together. I think it is called lap quilting or maybe QAYG. Often I use a different fabric for the backing on each section, or stray blocks. Then it kinda makes my quilts reversible. Only downfall is there is more hand stitching to be done putting back together but I find I get more done in smaller pieces.

Greetings,
The woman who does my quilting of backings when I took her two peices of fab, because I loved the two one being bargello the other a few yards of fab, suggested I seperate making two quilts because of the fab shifting at times. just something to consider. so each of my grand daughters ended up with quilts and everyone was happy.
Sandra whos frozen in Melrose NY

Wouldn't it be fun to do a great big D4P and use it for the back? I think that would be great, and you can always divide your backing into 4 quarters to do it with