My theory:
I work in the prepress dept. of a printing company and we have a bunch of old IBM RS/6000 model E30's that look an awful lot like parts donors for this thing. The E30's have 5 or 6 (I'm at home right now and can't remember for sure) half height drive bays in front at the top of the tower and they have very similar looking slotted pop out covers. I think it would be very easy to Photoshop in a slot for the cd and stretch a panel or two and paste in the power button. The handles look a lot like the hand hold on the front cover of the E30 as well. The rest of the case from the bezel back looks quite a bit like the case from one of our Intergraph Rips so I'm leaning heavily toward this being a clever little Frankenstein Photoshop effort. Oh and ours has a mylar sticker with the serial number on it in about the same place as the blurred area at the bottom. If I wanted to do one of these I would also do it in grayscale, print it out, wrinkle it up, wipe my ass and half tone the scan. If I wasn't so lazy I'd do just that and I'm pretty sure it would look just like the picture. I guess I could be wrong but that thing just screams RS/6000 to me. I have a lot of faith in Apple to come up with something much better than this.
I should say that I haven't been able to see the full size version of the picture, I've only seen the reduced size one.