MediaManager is a FlatPress plugin to delete uploaded file via admin interface. It shows a list of files uploaded with last modified time of file (this is in most cases the date of upload), size of file and the number of pages where file is in use. Permits also to manage subfolders ("galleries"), adding to/deleting files from them.
Extract zip content in your fp-plugin folder, enable the plugin in Plugins panel and look for "Media manager" under "Uploader" panel
Language packs and discussion on FlatPress forum http://flatpress.org/vanilla2/discussion/1099/media-manager-manage-uploaded-file