Hi there,
Sorry to hear that, it sounds like you will need to restore your forum from backup
I'm writing something and join this picture 
. A second later i decide to change it. So i delete it from my post and change it by another. The first picture always exist on public/upload/files
and can not be removed from the server. How to delete it and others ? i would remove files that are not used by nodebb.
with now nodebb 1.9.3 it's possible. wonderful !