1. All repositories need to filter their listings to return only files that are accepted by the current filepicker.

2. If we know that repository can return only specific filetypes, it need to define function supported_returntypes()

For example wikimedia lacks the code:

    public function supported_filetypes() {

        return array('web_image');

    }

and therefore this repository is displayed when trying to insert media into text editor.
Also, wikimedia lacks the filtering of the listing

$ret['list'] = array_filter($list, array($this, 'filter'));

which results in displaying images when looking for videos (and an error message when trying to embed it)

Note that many repositories fail to filter results!