The idea with the image is that you can't counterfeit all the little scratches and imperfections that makes every coin an individual of sorts.
Does all that show up in the picture?
That depends on the quality of the picture people upload. Here's an example of a simple 300dpi scan of 0.5 BTC coin (untouched by me, directly from a fresh roll I received from Mike):
http://certificates.0x0000.de/img/1217gngJgcC2PiCGB7xscVZ1yFsNgyNVQH.tif. I'm pretty sure if you show me a coin and this picture that I can tell you with good certainty wether or not the picture is of the coin.
Does a brand new coin have any recognizable scratches??
all the ones I ever scanned have discernable and many marks
It sounds more like a certificate of authenticity than anything.
I'm not playing devil's advocate here, just trying to understand the merits

What is a "certificate of authenticity" and what is it's significance? Who issues these? I'm not a coin collector, so if someone could explain how this works to me, I'd be happy. Sounds to me thats only something Mike could do and I think he will do something like this (sign with his pgp key scans of batches of coins). For old coins he can't do this, that's why he suggested to use "proof of age".
I'd say it's the proof of age that can be conducted that will potentially be valuable. The "certificate" I provide is just a nice addon you can appreciate or not.
I'm not playing devil's advocate here, just trying to understand the merits

Sure, no problem. I'm happy to explain my thoughts.