It’s often difficult to know when it’s ok to reuse an image and when it’s not. The internet may be a global network but each country has different copyright laws and there are no simple best practice rules applicable to everyone. The best thing to do is to use images that are clearly licensed for reuse. If you're in any doubt, choose another image.
(Information taken from 5 ways to find images for your website)
All images used need to be referenced or attributed
1. Choose a Creative Commons Licensed image - see Where to find reusable resources
2. Cite/Reference images from textbook/journal
Add these details underneath the image:
For more information (and exception rules) see Image attribution
If you refer to an image that you have found in a printed source, e.g. a textbook or journal. You must provide a reference for that source. The key is to use the proper referencing style attribution for the figures/images you use. All images must contain a legend or label which included the citation plus other information to help interpret/identify the image.
Figure 1: Circulation from Waugh, A. and Grant, A. (2018) Ross & Wilson anatomy and physiology in health and illness. Edinburgh: Elsevier.
(This example is Cite them right Harvard referencing style)
Figure 1: Circulation (3)
(This example is Vancouver referencing style - remember to add the full reference to your Reference List)
Cite Them Right will help you with Referencing styles and how to reference different resources such as books and journals