Here's a great website that features lots of skulls, skeletons and anatomical illustrations – these are in the public domain and are great for print on demand or any personal or commercial art project.
Skull t-shirts, skeleton prints and anatomy illustrations are a popular niche (check out Redbubble, Teepublic, Merch by Amazon, etc). You can clean up or modify these public domain images to suit your own artistic taste.
At the end of the video I have about a minute of mockup ideas (t-shirts, art prints) as well.
Timestamps:
00:00 Introduction
00:37 Copyright
02:10 Images
04:00 Downloading
05:58 Mockups
Links:
https://www.nlm.nih.gov/exhibition/historicalanatomies/home.html
#publicdomain
#tshirtdesigns
#craftystax