For our Forum this month, we were delighted to have Sharon A. Wright as our speaker. She demonstrated and showed many examples of piecing the backs of quilts. (She did mention not to piece the back if you're hand quilting, only machine quilting.)
She said she enjoys using up every bit of leftover fabric from making her quilts - especially if she knows she won't be using that fabric again.
She normally puts her quilt top on the floor, then just works in sections to make up the back. For us, she pinned it to the wall, so all could see.
She showed many examples, from extravagant to simple:
This side is actually the front of the quilt: