I’m skeptical that we can do anything in the wiki that would satisfactorily solve the problem.
I believe that the wiki should usually show only pictures and icons that commonly represent that key or tag, and not the actual rendering in different maps.
The task of showing the rendering of a key/tag in different map styles could be delegated to a website that shows several different map styles in parallel, given a coordinate or a tag (looking for a random object with the overpass api).
While I agree that using the wiki to generate or manage these rendering examples isn’t a satisfactory solution here, I’m not convinced that this kind of content has no place in the wiki.
In any case, the best approach imo would be to set up a website that aggregates rendering examples provided by the style/software maintainers themselves, similar to how Taginfo aggregates information for its “Projects” tab. But there’s still the possibility of including rendering examples on wiki pages as an iframe or such.