With version 2025.5 of JOIN Customer Contact, images can (again) be added to a call-back note or to tasks.
In the add callback note screen, click on the add image icon to add an image to the callback note.
The image will then only be shown in the sent email (depending on the template used) and in the Edit screen. The image will NOT be shown in the details screen of the callback note.
If necessary, adjust the template used when sending the callback note if images are to be used in the callback notes.