Jennifer,
yes in face to face classes, no problem showing images. But as soon as you videotape it or otherwise put it in the LMS anyway other than the original view, you need to ask permission. Especially if you are showing the artist's (creative) techniques, you need to ask permission. You are bound to receive it, no problem. And in an art class, any time you or student take that work and add to it, edit it, etc. You must have permission!
Renee Shaffer