As a teacher, I needed picture books at times to teach young children who were were behaviorly or mentally challenged what was expected in certain situations. There is a program that was used by speech teachers to get pictures for this sort of thing (I don't know the name) but if you know a speech teacher, you might ask if there are any kind of pictures on that program you could use. I also used pictures from
www.synonyms.net I put in all kinds of descriptions that I thought of for certain situations, etc. There may be other free, non copyrighted clip-art sites. Sometimes there are Spanish to English sites that are free and have pictures that might be used. I hope this helps.