Hi @Deborah.Amory, hope you are well! I saw this stock photo collection making the rounds, and immediately thought of whether it would be useful for your textbook: Gender Spectrum Collection of stock photos from Broadly of trans and non-binary folks doing everyday activities.
I believe the photos are licensed CC-BY-NC-ND and the creators also have suggested Guidelines for use.
I’m not sure whether you’ve already started think of non-textual elements to the book, or if this would be helpful, but wanted to share this with you as I had all the information handy.