If you send me pics of the interior and some of the material/colours you are thinking of, I'll see if I can do a mock up for you.
Just the standard GTI interior as the "blank canvass", but for the seats, a contrasting colour in the centre bits, leaving the bolsters anthracite, and the contrast also on the door cards, possibly where the leather already is. As for colours, I'm shyte at all that arty stuff, so I'll leave that for the experts to decide!