all good suggestions, I agree overcast light is best (no shadows). I have used thumbtacks to hang a top from the molding around a double closet door (put them in from the top of the molding to avoid visible holes. Or tack to an outside wall if possible. It depends on where you can hang your quilt and where you have enough room to stand back far enough.
I am amazed at how many quilt sellers on Etsy have their main picture one where the quilt is all scrunched up on a chair, or even folded!! When a buyer is sorting through thumbnails, the quilt picture should really stand out.