Comment Auditing and consequences (Score 3, Informative) 219
No matter what solutions you use for backups, the admin will be able to corrupt or bypass them in some way given enough thought and motivation.
However, for sane though disgruntled people it would be sufficient for them to have the common sense understanding that malicious actions will have strict consequences - people generally don't risk going to jail just to annoy a manager or company. And in the cases where someone would really be prepared to risk that, I'd rather worry about them coming to office with a gun, not tampering with a pile of pictures.
What was the aftermath of the previous cases you say of people leaving in anger and presumably doing something damaging? Your previous reaction in these cases forms the expectations in your admins about what they can get away with when leaving in anger.