Quilters have been inspired by each other's work since the beginning. That's how this art/craft began. I don't see how one can truly copy a quilt unless it comes from a kit which has all the fabrics pre-cut.
I have a large library of quilt books. I frequently refer to them for inspiration. While I may use a block that I find in one, I have never made a copy of a quilt.
I have taught a number of people to quilt. While we have referred to quilts or blocks in a book, no one has ever made an exact copy.
Even if someone were to make an exact copy of one of my quilts, I would be flattered and amazed at her ability to find all those fabrics.
As even the book referenced had no pattern, the quilt was obviously included for inspiration. Other than looking at the photo, what more is there to do? Anything that arises from viewing the photo would have to come from the maker.
Let's say, for example, that the photo is of a quilt which features a tree with falling leaves. There will be a sky background, some ground cover in the foreground, and perhaps some rolling hills fading into the sky. Based on just this description, there are many ways to construct this image. I'm sure that in reading it, you have constructed a mind's eye view of your colors, layout, and maybe even fabrics. Yet each of us will have seen a different image, and in the making of it, may come out with something different from our original concept. Is any of this cheating or stealing? I say no. I have merely given you an idea, and ideas cannot be copyrighted. So, if any of you wish to make a quilt based on my idea, I say, "Go for it!" I'll even start a new thread where we can post photos of our results. Who's up for it?