Plan your back carefully so that it seems to carry on the theme from the front. Otherwise, it just looks like, well, leftovers. You paid a lot for that fabric on the front. Make sure you can be just as proud of the back. Poster
QuiltE has really interesting backs. Even that totally scrappy one looks planned somehow.
I've done several quilts that use 2 different fabrics (not enough of any one) which went across the width. I have only done one
pieced back using multiple fabrics. This was a quilt-as-you-go quilt that I did section by section and the placement reflects that. Its not nearly as interesting as Equilter's though.