Forum Discussion
Re-reading my reply, I should perhaps add that most of us buy our stock images under a "single-use" licence as it is much cheaper. i.e. if you purchase images using a Shutterstock monthly "plan" and download an image under that plan you are purchasing a licence to use that image for a single project.
We are always at pains to point this out to clients when we supply source files (which is most of the time). They can modify the course and use selected images from the course as thumbnails to promote that course BUT they are in breach of copyright if they then take an image from one of our courses and use it in a different course without paying a new licence fee
To purchase an image "royalty-free" is generally way more costly and we do it only when the client requires that image for multiple projects.