My first quilt top was scrappy with purpose, in that I cut out all the squares of fabric I just 'happened' to have and then arranged, sort of in 9 patch, before stitching together.
My current quilt project is a BOM. So the fabrics and pattern are chosen for me. I am also doing alternates in fabrics of my choosing on the same pattern. The BOM is various blues with neutrals and complements, and on my alternates I choose similar groupings (focus fabric with neutrals and complements).
I have future quilts in my head that are primarily focused on fabric and I'll have to find a pattern that works (I have a denim in mind and a 'clothing nostalgia', etc.)