Images created in SVG, handcoded for the most part. Many of these images are available on openclipart.org as well. Some are remixes of openclipart images, where part or all of the original openclipart is included, then handcoded from there.
I volunteer at schools teaching students grades 4-12 how to code using SVG and have lesson plans for teachers on my website http://steamcoded.org as well as some applications of SVG in STEM and STEAM
SVG is a great way for students to learn Math, Art, and Coding. It's fun and creative.