So system img , vendor img, and boot thats it.
To make a full backup of your ROM, at the very least, backup these:
Boot
Data
System_Image (or System - only if System_Image is not available for backup), and
Vendor_Image (or Vendor - only if Vendor_Image is not available for backup)
You might also wish to backup the Internal Storage.
You should also have at least one good backup of Persist_Image. Note that you should not restore a backup of the persist image, unless it proves absolutely necessary (and it would be highly exceptional for this to be the case). This backup is only an insurance policy for the extremely rare situations when disaster has already struck, and all well-informed advice is to the effect that only restoring "persist" can fix the problem.