A little off topic, but which back up camera are you looking to install? I want to do the same when I upgrade my head unit to an Eonon.
1)
Car Reverse Rear View Backup Camera for BMW 3 5 Series x5 X6 | eBay Not sure how the much light will be emitted from this one, I love my led license plate lights.
2)
1999 13 BMW x5 E53 E70 CMOS NTSC Car Rear View Backup Reverse Waterproof Camera | eBay Not where to install this one.