Recently my wife got me a bottle of nitrogen for nitrogen beers and coffee. To have the ability to serve on both nitrogen and CO2, I decided to move my tanks outside of the fridge. To do this I picked up a 35x35x70 cm IKEA EKET cabinet.
http://www.ikea.com/pl/pl/catalog/products/90333938/
It goes together easily without any tools, and I used a blade knife to open a hole in the back for the lines.
Two tanks with single gauge regulators fit snugly. Lines out the back. I attached a 3/7 by 3/8 John Guest and 3/8 John Guest Tee so I can quickly swap my tanks out without issue.
I purchased some 3/8 x 3/8 John Guest bulkheads, thinking initially I would install ball lock fittings inside I realized the strength of the fridge would probably work better with these:
After removing the fridge, I used a 20 mm spade bit to open up holes for the bulkheads. They screwed through the hole perfectly, not sliding in and out but catching with the threading.
I cut away as little insulation as possible and snugged the nut down to screw into. It took two screwdrivers to hold the nut in place while my wife screwed in the bulkheads from inside the fridge.
Once the bulkheads were installed, I hooked up some small lengths of 3/8 tubing to fit into the fittings shown earlier between the bulkhead and regulator.
I hooked up the fittings and then began putting the kegerator back together.
The lines are hidden easily and can't be seen from the front at all.
The gas lines and ITC-308 controller from the back:
Once it was back together I oiled the top since everything was off it and got it ready for my next beer (and soon coffee).