You can adjust the brightness of the internal LED lighting already.
Not heard of anyone getting any data up on the main screen though. Or any other fancy changes.
There are plenty of changes you can make with
VCDS (or other plug in modules) that improve things though. And I think many of the adjustable things are still undiscovered.
I coded the following on my car:
tailgate close with remote
tailgate close with button on door
stop handbrake coming on when you open the drivers door
rear lights on with DRLs i.e on all the time
front DRLs can turn off from MMI
turn off seat belt warning chimes
make handbrake release when you press accelerator even if seat belt if off
make start / stop remember the last set mode so I don't have to turn it off every time I start the car
start /stop LED inverted so it is on when start / stop on rather than when start / stop off
Video in Motion (had to get someone else to do this for me)
I'm sure there is more but can't recall them all. The one that I still really want but haven't figured out yet is to stop the warning beeps when you open the drivers door with the ignition / engine on; really annoying. I know you can press the left button on the steering wheel but would like to permanently silence it.