Same issue, but add .HEIC, .tiff, JEPG-2000 as not sending 'Message failure' issue.
work around is [from the finder] to click on the picture to highlight, go up to the menu bar & click on 'File' & down to 'Share...' & select Messages from the list.
OR just right-click on the picture & select 'Share...' from the drop down menu & then select 'Messages'
but then again - I do not a work around, I want to drag & drop into the messages window, directly, like I always have.
I found a solution from another Apple Community page :
Macbook not sending pictures in IMessage … - Apple Community which I am trying next. I have 'messages saved to the cloud' turned on, so nothing is lost & maybe if the database is not rebuilt automagically, then I'll just resync from the cloud & all is good again. hope this helps & works for you. Cheers!