So if it were me, I would probably advise the client to get someone to mockup up the comforter in a 3D modeling/rendering environment that would allow UV unwrapping. This allows flat images to map onto a 3D surface—in the right hands it is very convincing. You would still need photos to aid with the modeling and provide the room/light. Since the modeling requires quite a bit of work up front, it's probably not cost effective for only a couple variations. But if they are going to need a lot different designs, this will be quite a bit easier in the long run.
I would definitely agree. Wrapping a pattern onto such an organic shape in photoshop convincingly really wouldn't be easy. But mocking it up and UV mapping while much cheaper for multiples still won't be cheap, but will give a far better result.