Here are a few image sites that are approved for Educational use and are not blocked by the Smart filter

google images safe search
safe searching on google images - this is a link to a safe search for google images. It will take you to pictures of cats, but you can enter a word to searh to find other images.
Pics4learning.com
Edupics.com
Teacherfiles.com
School Discovery clipart
Animal pics
Stock Photography
210,867 Searchable Stock Photos & Illustrations
Civil War Images
Landscape Architecture Image Resource
Includes photographs of countries, places, and architecture.

Hubble Site: Gallery
Includes images of deep space objects and space shuttles.

Sonoran Desert Jpegs
Includes images that can be used for biology classes. It contains photographs of flora and fauna of deserts. NOTE: The site leads to websites with ads.

Entomology Image Gallery
Includes images of beetles, butterflies, mosquitoes, bugs, and more.

Governmental images
Includes images if the capitol, monuments and memorials.