Awesomesauce.
Yes, I have seen it before, but as shelley said, it looks much better with gray plastic.
Lol, it'd be even better if the corners were enlarged, but is that possible?
I think Andrew Kang has done it.
But like previously stated, yours looks very nice!
Also, I once met companion cube at an anime convention, took pictures too~
EDIT: Yeppers, I just looked on his facebook, and he's done this on a black cube.