Because it’s hard to make nice figures when you don’t have access to expensive software like illustrator! Here is a list of resources that can help you make the best figures possible without breaking the bank because they’re free!
Servier Medical Art – Free downloadable images so you don’t have to spend hours making them yourself!
Inkscape – Similar style to illustrator, allows you to draw your own figures!
Fundamental of data visualisation by Claus O. Wilke – good resource for learning more about how to present data.
R – for plotting data and data visualisation
Somersault1824 – (Not actually free but pay what you want) for great images
GIMP – Another free image manipulation program as an alternative to illustrator