Here are a few I use:
http://www.picsearch.com/ (kid friendly image search -( not necessarily open source but could meet Fair Use rule)
or we often go to Google Image advanced search and set to strict filter and filter usage rights for "labeled for reuse"
From: School Information Technology Discussion [[log in to unmask]] On Behalf Of [log in to unmask] [[log in to unmask]]
Sent: Wednesday, April 28, 2010 6:38 PM
To: [log in to unmask]
Subject: open source images for elementary school
We are looking for open source images for elementary school. We're doing a 7/8th project on Perseverance. It will cover topics such as the Holocaust, slavery, Japanese concentration camps, and women's suffrage, Arizona's new proposed law. We've looked at wikimedia, but are running into some inappropriate images on the websites (nudity). I would like to find something age appropriate. Suggestions are greatly appreciated.
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The St. Johnsbury Elementary School
257 Western Ave - St. Johnsbury, VT 05819
802-748-8912 Fax: 802-748-1095