Scrappy can mean so many things. The most recent one I did used lights, mediums, and darks. And there was a method for combining them.
http://www.quiltingboard.com/t-81391-1.htm
Another one I did was a Civil war fabric scrap quilt. It would not have worked if there were novelty or children's or bright colors thrown in. However, it did have over 50 fabrics.
http://www.quiltingboard.com/t-39328-1.htm
I think that picking out a pattern first has helped me make scrappy quilts. Knowing which pattern then helps me organize my scraps and use them to get a good effect.