This blogpost contains links to resources that can be freely reused.
Pictogram collections (collected by Helena Jambor)
https://bioicons.com (bio)
https://smart.servier.com (medical)
https://healthicons.org (medical)
https://www.phylopic.org/ (animals)
Copyright free images:
More information
- https://www.tudelft.nl/library/copyright/teacher-copyright-answers#c1132165