Just because a picture/image is on the Internet does not mean it is free to use by all. Watch the video to the right by Royce Kimmons or read Creativity and Copyright, A Quick-Guide for Students and Educators by Connect Safely for details.
Ask yourself or your students, how are you using the images, information, etc?
Public Domain: belonging or being available to the public as a whole, and therefore not subject to copyright
Openly Licensed Educational Resources, OER
Where to find Public Domain or Creative Commons images.
Where to find royalty free music
Where to find Openly Licensed Education Resources