I helped create an Autism support group website several months ago. I needed some Autism related clipart and tried to find some of the colorful jigsaw puzzle pieces that are often found on Autism related sites and accessories. I didn’t find any that were suitable or in the public domain and decided to create my own. I found a single puzzle piece on the OpenClipart website. The OpenClipart website has lots of public domain clipart in SVG format.
Using Inkscape, a free and open source graphics illustration application, I fit four single puzzle pieces together and colored them. Then I fit those four pieces together until I had a small mat of puzzle pieces. I tried to match the color scheme with an Autism ribbon that I had seen. I exported the small mat into PNG format. I used the GIMP, a free and open source image manipulation tool, to add several of these together. I ended up with an autism puzzle background that I could create shapes or words in using the GIMP and masks.
I never did use the words on the website. I did use the small four puzzle piece on the website. The Autism puzzle piece also seems to be a popular search term for that site.