the first 20 lap quilts i made for family i designed myself and used embellishments and some geometric cuts of fabric. as a matter of fact i don't think i have ever really 'used' a pattern. i reverse engineer a pattern like artsyone mentioned below. i look at pics, choose elements of quilts i like, figure out the blocks and then make them from my own aesthetics.
i enjoy the creative process that way but i must say i have been sewing since like forever and have always sort of combined details to create my own unique garments. there are those who have no desire nor inclination to design their own quilts and will always want to use patterns and then there are those who like to design or include their own elements to established quilt patterns. there is room at the quilting table for all of us.