Wikimedia Commons

The Wikimedia Commons is a project that provides a central repository for free photographs, diagrams, animations, music, spoken text, video clips, and media of all sorts, used in pages of any Wikimedia project.

If you want to use images from any Wikimedia project on another project, dont double upload, upload once to Commons instead, thats what its made for.

Also this is a great source for searching images that you want to use on your own websites or publications without the copyright trouble.