There are so many different weights of fabric sold as "upholstery" fabric. There are light weight cotton that would be perfect for draperies and "light" upholstery. I would definately wash some of the fabric to see how it will hold up with laundering.
I have made quilts out of these light weights.They are usually wider and some have a stain resistant sheen. Don't be afraid to experiment with different fabrics. It fun to create something different or unexpected. I quilt because it's fun for me. :D
Ditter