OJS 3.1.2.4 - How to manage images added by the "JustBoil.me"?

How to manage images added by the “JustBoil.me Images Plugin” (TinyMCE), e.g. to Announcements?
In the “html/public/site/images/[user_name]” folder, unnecessary images accumulate. How can I delete them?

Regards
Wojtek