Interesting to see pcper call it 'abuse of graphics cards'.
Source
http://www.pcper.com/news/Graphics-Cards/Curious-where-all-those-AMD-R9-graphics-cards-are-going
What you are looking at are six MSI Gaming series R9 270 cards running through the aid of PCI Express to USB 3.0 riser cards.
You can see the rest of the photos here and if you want to see more of this kind of abuse of graphics cards and you can also check out the Litecoin Mining subreddit where this was sourced.
Source
http://www.pcper.com/news/Graphics-Cards/Curious-where-all-those-AMD-R9-graphics-cards-are-going