I always try to coordinate the back with the front. I don't want to have a lap quilt that is pale blue on the front and an assortment of wild fabric colors on the back. I want it to be a "complete" quilt that will look nice no matter how they wrap it around themselves. I use fabrics from the front, although in larger blocks as has been mentioned. I haven't run into any problems keeping both the top and back lined up. (knock wood!)