I found this website
http://educators.mfa.org/vts-mfa-image-set-404591. It has a ton of images that you can use to have the students look at through the Visual Thinking Strategies. The nice thing is that the site offers questions for the teachers to really get the students insights on what is happening in the pictures. These could be used for any subject area and could be a great introduction for the students to get into a unit. VTS is a great way to get the student's minds working!