I can see this error message in the console:
Failed to load resource: the server responded with a status of 403 (Forbidden)
But when I access one of those images directly (e.g.
https://www.spheniscus.brennik.fr/lib/tpl/spheniscus/images/logo.png) it's a 200.
I guess it must be some setup issue on the server. But I don't know much about that, sorry.