I almost always piece my backs. I try to make it so that the back doesn't have to line up with anything on front. I haven't had a problem going over the seams, either with my DSM or my longarm.
Here are two of my more intricately pieced backs; both have log cabins on the front. The first was quilted in sections on my DSM and the 2nd on my longarm.
http://www.quiltingboard.com/t-23612-1.htm
http://www.quiltingboard.com/t-82165-1.htm
And here's one that's not so intricately pieced:
http://www.quiltingboard.com/t-22410-1.htm