[kf4eok]

I have the same problem and I have tried both a 0 and 20 with the same results.
Admincp > options > Message Posting and Editing Options > Maximum Images/Videos Per Post
Has anyone found how to resolve this?

--------------- Added [DATE]1497245174[/DATE] at [TIME]1497245174[/TIME] ---------------

I found the solution. My problem was in the usergroup settings.

Did you set up all settings correctly? For images, there are (at least) 2 settings you have to take a look at:
AdminCP > Settings > Options > Message Posting and Editing Options > Maximum Images/Videos Per Post.
AdminCP > Usergroups > User group Manager > [Edit Usergroup] > Maximum Attachments per Post.

All of these settings are set to '5' by default.