"Embedded files" (repository_areafiles) plugin allows to re-use the files embedded in the current text area.
To install: copy folder areafiles to <rootdir>/repository/, login as admin and run upgrade script.
To use: Open any form with textarea in HTML mode, insert an image using filepicker as usual. Click "insert/edit image" again and in filepicker window select repository "Embedded files". The list of all files used in this textarea will appear and user can re-use any of them.
You can insert media and/or links to other files as well. Note that files in filepicker are always filtered by the accepted file types (for example when you add an image you will only see images even when other files present in area).