If you click on them, many images on Wikipedia will lead you to their parent page on Commons (click “view on Commons”). Ideally, that’s where all non-copyrighted WP files are placed (unlike those that are under copyright, which limits in how many places they can be used).

Literally the only wiki-based media repository out there.

There’s also monoskop.org (although unlike Wikimedia Commons it doesn’t seem to care about copyright law too much).