backup/restore of course image

We're noticing the course image (which nicely shows up on the dashboard in some themes) isn't part of the backup files in our testing.  We're on Moodle 3.6.5 currently (and will be going to 3.8.1 this summer). 

Has backing up the course image become part of 3.8.1?  Is it not part of 3.6.5 or are we not seeing it?

thanks,

Scott