https://forums.realmacsoftware.com/t/cms-random-image-links/56234/3?u=upssjw
You do this with CMS, setup is fairly simple, currently not working in the latest update, Elements moved to CMS 2, but should in the next update 
https://forums.realmacsoftware.com/t/elements-cms-2-is-here/56224/60?u=upssjw
There a 3 examples in the project, 3 and 5 images but could be more, I can help if thats the way you chose
the first page has a very small custom component (free), the second page is Elements components with a very short Twig snippet
you can refresh my test site, to see it working, no thought in the page design, the two pages do something different to display
https://sjwjaw.co.uk/randimage/