quiltingshorttimer

No, there are other widebacks--flannel, sateen and other cottons. When long arming I prefer a wideback as you don't worry about front/back seams causing a bump in the machine tracking. Plus the wideback, once squared, stays that way on the frame and lays smoothly. And the cost is about the same, or even less, than using LQS fabrics pieced.
As with ALL backings, widebacks need to be squared up before quilting. And some, especially the thinner muslins or flannels, should be washed before use due to shrinkage. One complaint with piecing backs I've run into, is that it seems that quilters sometimes piece together a "hodge-podge" of left over fabrics--many these are not squared up and sometimes have the cross and long straight of grain mixed, so that the stretch that occurs while on the long arm (or even under the DMS foot) can leave pucker possibilities. The only backs that I've had pucker/tuck problems with have been pieced with these issues. So if you are going to piece chunks of fabric together, I'd suggest that you be sure to square the pieces as you cut, to seam with the grain matching (cross OR length-wise) and remember that your backing acts like the foundation on a building--if it's not "solid" the top will be distorted.