It's probably not "usual" to make a black quilt, but when I made it, back in 2005, I had been collecting novelty fabrics with black backgrounds for some time. I happened to mention to my son I thought they'd make an interesting quilt.
I wanted to make a quilt where the individual blocks disappeared. I wanted the viewer to see colors dancing across the surface then to notice there were dozens of different fabrics, then to notice the quilt was patchwork.
You can read about the process I made it here.