Way back in the dark ages (C5.6.x.x!) I had a free plugin called Wall Gallery that allowed me to display a file set on the page. A lightbox slideshow is triggered by clicking on the photos. Is there an C8.5.x.x version available anywhere?
It isn’t in the current v9 marketplace, but there are plenty of alternatives including my own Omni Gallery.
Do you have a legacy version that works with C5.8.x.x?
Omni Gallery up to v1.9.10 was primarily developed for Concrete v8.5. After that, back compatibility was not tested, but was also not excluded through to Omni Gallery 9.2.29 when the minimum core version was set at Concrete 9.1.3.
The current latest version available directly through the marketplace is 9.3.0. I can supply zip packages for older versions of Omni Gallery on request.
You might be able to use the ‘Magnific Popup’, which I think is the core of 8.5.2. then try looking at an old ‘stack overflow’ post to help?