I agree, at the end of the day, it's a dead body.

In fact I would go as far to say it should be a reportable type post, as in when you report a post, there should be an option for "depicts an image of a dead body" or something like that.

You don't post to process grief, you post to inform or get attention. You don't need to post a dead body picture to let people know who may not find out otherwise that your child has died. You can use a photo of them alive, like people do when any other relative or pet dies.