It was suggested to install the FileImporter extension on wikis that allow to have media that are not allowed on Wikimedia Commons. E.g. English projects allow fair-use media like (small-size) movie screenshots and cover art (books, music CDs, movie posters). These wikis still want to share these media, but can't use Commons.
Another solution for the same problem would be a dedicated media repository for non-free media, and allowing imports to this repository. This was most certainly already discussed on Commons and wikis that have this problem. TODO: Investigate and collect links to previous discussions.
User requests for such a feature: