I add this to the 'Non-image Attachment' thread after you had marked it as resolved, so just posting agin to make sure it gets noticed - sorry if that means you get it twice.
If I have this right…
This is about using a generic image for say a pdf file as an attachment.
So if I use
echo $attachments->image( 'thumbnail' );
and the attachement is a pdf, then the generic wordpress image should show.
Sadly it does not.
If I have got this wrong… then how do I get the generic image to show?