I use magazine pictures and also calendar photos for the students to use as
reference material. It makes such a big difference in their work when they
see a photo as opposed to drawing from memory. An example, drawing a horse.
Can't bring a real one into class and by looking at a photo one can see the
shapes of the ears, face, the rounded cheeks of the horse. I don't think it
is plagiarism or cheating because the final drawing is their interpretation
of the horse, not a copy of the photo.
BTW, I teach k-5. HTH