I have used board-maker on numerous occasions, but only when I think the images would be developmentally appropriate. For example, I do not use it when making materials for teens with what we used to call "Asperger syndrome" or "high-functioning autism." For those kiddos, I usually tailor the stories and pictures to their interests and get pictures from Google images.
My colleague Allison Randell at the University of South Carolina found a graphic design service to make some really exceptional visual supports. I believe the service was very reasonably priced as well. Allison is a post-doc for Michael Beets in exercise science/public health if you want to look her up! She is also listed as a collaborator on my page.