Many of the big portals for Kid Search have nearly abandoned their specific Image Search in favor of more broad search results not specific to images only. Take Ask Kids and Yahoo Kids for example. You will no longer see an Images or Pictures button on those sites. However, the list I've compiled below presents a pretty thorough list of resources that will work. Let me know what you think:
Pics4Learning: http://www.pics4learning.com/ A good collection of categorized images from Tech4Learning. Nicely filtered.
PicSearch: http://www.picsearch.com/ An excellent image search with over 3 billion pictures. There is nothing stopping a kid from typing the word "nude" into the search, but the results would be nude paintings instead of pornographic photos. Much more filtered than a typical non-safe Google Image Search. This Swedish image search engine says "Under no circumstances is it possible for children to bypass our family filters since they were planned for from the outset and integrated into Picsearch's whole indexing system. Offensive content is easily eliminated by our specially designed filters before it can even enter our database." Also, this resources was recommended by a few school librarians in Google Answers, so I tend to trust what they say.
KidsClick!: http://kidsclick.org/ Scroll down and click on the Pictures button for a list of the best resources for pictures by topic. There is also an alphabetical search.
Kid Clicks!: http://www.kidclicks.org/index.html This makes sure that Google is using only SafeSearch results.
TekMom's Search Tools for Students: http://www.tekmom.com/search/ This is a nicely-organized list of Search Engines for kids from TekMom. This might be the best of the bunch, since it is so nicely organized. Put it at the top of your Favorites, for sure!
10 Search Engines for Kids: http://www.makeuseof.com/tag/10-search-engines-kids-parents-safe-browsing/ A nice list of 10 by MakeUseOf.com but it's not specific to images only. Just search engines for kids. Some of the screenshots are a bit outdated, such as Yahoo Kids and Ask Kids, but you get the idea. And I love MakeUseOf, so I had to include this.
Ask Kids: http://www.askkids.com/ This used to have a button for Images, but no longer. Now you can just search a word or topic and it brings up filtered search results. There is a Movies button.
Yahoo Kids: http://kids.yahoo.com/ Yahoo Kids does not have an image search built in. Yahoo's Image Search has a SafeSearch built in and turned on by default, but that can (like in Google Images) be turned off in the Options>>Preferences.
Kid Safe Image Search: http://kidsafeimagesearch.com/ This is a good idea, and it definitely comes to the top of any Google search on this topic, but as of right now, it DOES NOT WORK.
If you have any favorite kid safe image search tools, please let us know about them.