Is this around what you might be possibly asking about?
A PHP file that would manage your image/file requests.
So, a http request to
Would be dehashed and addressed to
Look here for inspiration and further search keywords
The issue is that once the image or its cloak has been served to the greedy internet, the toothpaste is already out the tube.
Your bestest bet is to nip the issue before it is an issue.
If this were an issue for me, I'd force all uploads through a PHP script that renamed the files right there on the server.
So that, my-wifes-maiden-name.jpg before upload becomes 2323232332u32iu3823u23u2832y38y823u82832832832323.jpg on the server.
And of course I'd lock up access to that folder to prevent renaming or some sort of mishap.
But it seems you might be dealing with an already established system ...