It is fair use, whether it is known or unknown. You can copy Van Gogh's Starry Night, or the Mona Lisa, or I'm looking at altering Rosie the Riveter to be Rosie the Quilter.
I always believe in attributions, doesn't have to be in the label, but "I was inspired to make this by a photograph" is enough. Sure, nice to give someone a nod but this is your quilt, not their photo.
Here's a nice breakdown
http://www.tabberone.com/Trademarks/...Quilting.shtml
Here's a special Canadian one
https://canadianquilter.com/wp-conte.../Copyright.pdf