I wrote an article for Interweave on modifying granny square garments. I used the Maggie Wrap from Blueprint Crochet as the basis. I hope it gives you some inspiration on modifying all the projects in the book. If you have made one that you modified I would love to see it and feature you on my blog. Let me know!
Don't forget you can get the pattern free over at Knitting Daily. Keep in mind it is an excerpt from the book and is written only in symbols. If you need a symbol refresher, I would check out Blueprint Crochet first before attempting.