I have done one quilt with a coordinated design on the backing (like one huge block) and it is like giving two quilts in one! So if my DS gets sick of the stripey patterns of blues on the front, he can look at the large, restful blocks of blue on the back.
If and when I get good enough to FMQ something pretty to look at, or something well enough constructed to invest in a long-armer to do it, I'll go solid color or white. By then maybe somebody will say I'm a 'real' quilter! LOL