Kathleen Loomis' book "Pattern-Free Quilts, Riffs on the Rail Fence Bock" arrived today. I read about it in Uta Lenk's blog and found it very interesting. Kathleen Loomis is a very skillful artist and she has been working together with Nancy Crow.
In one of the chapters, "Making Your Pattern-Free Quilt", she is describing how to sketch out possible block arrangements in black and white before starting assigning colors and also how to add degrees of complexity by varying the angels and turning blocks. Another chapter is "Putting Your Blocks Together" with lots of useful tips and suggestions.
You can order your own copy from https://www.createspace.com/5403666 and read more about Kathleen Loomis in her blog Art with a Needle. I'm sure this will be one of my favorites.