The photo fabric products that I've used were very substantial, not needing interfacing at all, and didn't require any attention other than immersing in cool water after printing. However it is important to find out what method your friend used for the photos, and whether they require any special attention before you sew them into the quilt. Even then, it might be a good idea to wash one of the photos, just to see how it keeps its color. It would be a shame to put them all into the quilt only to find out that the color doesn't last.