If you think about it, any quilt is reversible. Some just have more interest on the back. Quilting two tops together can be more difficult several ways. Keeping them straight and lined up can be hard, especially if you are sending the quilt out to a longarmer, who may not understand how you want them to line up. If you're not longarming the quilt, then the additional seams will add some bulk that might cause problems on a DSM. Here's a quilt that I did that had two tops -
http://www.quiltingboard.com/picture...k-t216883.html I've also pieced some backs to the point that they might as well have been tops -
http://www.quiltingboard.com/picture...rs-t82165.html