Well, I would think the thing to do there would be to put holes for a Standard VESA wall mount, then either put stick on feet over them for desktop use, or even better, get screw in feet. This way, desktop users could leave in the feet and have a "pizza box", 'hide everything' users could mount it on the back of their monitors, AND the uber-nerdy could mount the thing on a swing out VESA wall-mount.
I assume that you would be putting feet on a "pizza box" case anyway, so it doesn't seem like it would be a huge deal to have that be where the holes are.
Extra Double Super Bonus points if you could design it so that not only does it have VESA wall-mount holes on the bottom, but so that it was built in a way that allowed it to be mounted BETWEEN a monitor and a wall-mount while still being structurally sound and attractive enough for use on a desktop.