Judy Martin has an interesting "almost wedding ring" quilt with no curves: it's called Monet Wedding Ring, and you can see a picture here:
http://www.judymartin.com/gallery/wilber3.html
It's in one of her books,
Scraps,and she did it in all kinds of colors (the colors of Monet's garden), not the green and light one pictured here. It is spectacular!
If you google the images for 'monet wedding ring,' you'll see many versions of it.
Jory