Copyright-Free Images via Google, K-12

Here’s how to find images on the Internet that can be copied and modified.
http://www.google.com
Click Images (top left)
Click Advanced Image Search
Enter search and go to Usage Rights pull-down
• Labeled for reuse
Your results will only include images labeled with a license that allows you to copy and/or modify the image in ways specified in the license.
• Labeled for commercial reuse
Your results will only include images labeled with a license that allows you to copy the image for commercial purposes, in ways specified in the license.
• Labeled for reuse with modification
Your results will only include images labeled with a license that allows you to copy and modify the image in ways specified in the license.
• Labeled for commercial reuse with modification
Your results will only include images labeled with a license that allows you to copy the image for commercial purposes and modify it in ways specified in the license.

OR
http://www.google.com
Click Advanced Search
Enter search
Click Date, usage rights, numeric range, and more
Choose Usage rights in pull-down menu
• Free to use or share
Your results will only include pages that are either labeled as public domain or carry a license that allows you to copy or redistribute its content, as long as the content remains unchanged.
• Free to use, share, or modify
Your results will only include pages that are labeled with a license that allows you to copy, modify, or redistribute in ways specified in the license.
• If you want content for commercial use, be sure to select the appropriate option containing the term "commercially".