I read about the X-Ways software that was used to forensically examine the proof of life photos. It is very good. It can tell many things about the EXIF data and the JPEG data.
It looks at the condition of the file, if the file is complete (hasn't lost data), trailing data (if data was added), if JPEG data was retroactively removed with a tool, if it was cropped, if the amount of 'slack' present is what should be expected from the photo source, if the jpeg file is rewritten by an editor the 'slack' disappears, the field sensor size (when a photo is reproduced), the processing state (camera, editor, or content management system) .... among other things.
Just mentioned a few of the things it forensically looks at, to give an idea of its capabilities. But there is much more in this link.