Including the art, rather than linking to it
In the description section on this page, there are two text links to cave art. Seems to me we could include these on the page, something like what I've included here.
This may challenge our layout ability, but may offer a richer experience for the learner. I suggest considering this as a design principle for the course which we can put in our style guide.
If the images are openly licensed - -my preference would be to include them in the course materials. This is useful for learners who may not have reliable or expensive internet access and could use a print-version alternative.
It may require a little "padding" text to assist with layout but better in the long run imho.