I think it has alot to do with the type of top and how you will quilt it. I like fabric that is light and little pattern if I am sending it out for quilting..as I want to see all the beautiful quilting stitches. If its something I will quilt myself and I am not so confident on my quilting or its not anything outstanding planned for the quilting , I use a print with colors from the top for my backing fabric. I do try to stay within the style... traditional, contemporary ..But large scale prints make fabulous backings as you can see all of the print.