This is a remix of daftmike's case. I had trouble printing his case due to the wall thickness, so I completely redesigned the case. It is the same as daftmike's except that the cartridge door is fixed and doesn't open and it dosen't have a second mini usb port. I have reused his buttons, cover pieces and LED lens.
Both the top and bottom case files have built in support.
I use Recalbox (https://www.recalbox.com/) as the operating system as I find it better than Retropie. The power and reset buttons are both functional as is the led. Recalbox has a script built in that allows you to use a switch to start and stop the raspberry pi (https://github.com/recalbox/recalbox-os/wiki/Add-a-start-stop-button-to-your-recalbox-(EN)), the LED is connected to the serial port TX pin so that it gives you a real power indication light. The reset button is actually the "ESC" key on a keyboard, I have used the circuit board from an old keyboard and wired the switch across the "ESC" key contacts (in my case it was a wireless keyboard, but any should work).
One of the two port usb connectors mounted on the Rpi needs to be de-soldered and relocated or you need to purchase a new one and wire it up. See Daftmike's blog for details.
All you need to do is put it all together and then load up some ROM's and have fun.