I am not a lawyer so I can't speak about copyright laws, but I think you can find the correct answer by asking yourself the following:
You have designed an original quilt pattern. You have done all the calculations, written instructions, copyrighted your design, gone to a printer, and packaged your pattern for distribution. You see your pattern for sale at one the vendor booths at your annual Quilting/Sewing Festival. They in fact have a sample of your quilt design hanging in their booth. Below the quilt they have your pattern available for sale. Up walks a customer who admires your quilt design, inquires about purchasing the pattern, but ultimately decides that by taking a picture of the finished quilt she surely can copy your design on her own and save herself the $8.00 for the pattern. How would you feel about this?
I appreciate the many designers out there that make it possible for me to purchase a pattern to make what I feel is a beautiful project. (I have drawers full of patterns to prove it LOL). Have I printed the pictures of some of the quilts I've seen on this board..of course, but not in an effort to copy them but to use them as inspiration for color combinations I would never have thought of on my own. I have designed a few originals myself; tablerunners, placemats, and walker bags. It has been suggested to me that I should print them to sell them. I've chosen not to do that because of the expense involved, and the likelihood that they would be copied anyway.
Please think about "copying" someone else's work. Enough said.
p.s.
I have attended many Quilting/Sewing Festivals and taking photos is prohibited for this very reason.