Most of my quilts have solid or ToT neutral color backs with a contrasting thread so the quilting really pops on the back. I've done a couple of pieced backs - mostly to use up small amounts of fabric i had left over from the top. I have a couple of quilts that have a white back that I had white thread put on the back for a special effect. Sometimes the top has a different color thread than the back. Sometimes I have the top thread matched to the top and even to the blocks so it seems sucked into the top. Sometimes Not. Seams? Whichever way they fit :-) All of the above are decided based upon the look and feel of the quilt top once it starts coming together. and selvages are always trimmed off. All of my quilts are LAQ'd.