I agree with everyone here, one person's scrappy may not be another's. A few years ago I decided to make a "green" quilt for my son, who has green eyes. It had over 200 different green fabrics and 50 or so background fabrics yet looked very unified because it was basically a two-color quilt. To me, it qualifies as scrappy but maybe someone else would say, No, there's only two colors in it.
I frequently do scrappy quilts and pick the fabrics by a theme -- fall, or all solids, or all brights. When I do make a "grab and go" scrappy there is still some organizing factor to pull it together -- the solid diagonal stripe in string quilts is an example, or a consistent background. Otherwise they are not enjoyed as much by my family, which is where most of my quilts end up. The quilt in my avatar is an example -- a wide variety of fabrics, but the consistent black and white pulled it together.