Don't paint bumpers black, there is a product I have which you can spray on rubber and it makes it look much blacker and newer.: I know what stuff u mean, i shall search it up! thanks
Get projector headlights before installing HIDs (like the ones Jalicno posted). I don't know about NL, but in UK it is illegal to have HIDs without projectors (the ones with the glass ball in).: Here in holland it is not illegal, and those projectors are to expensive :p so thats on the wishlist.
Swap the trim (i.e. rubber strips) for GTI trim or body-coloured trim.: Good idea! shall think about it!
Get colourless indicator lenses. thought about it, but those things are stolen 9/10 times here where i live.
Get one of these: i love those, but also to expensive, are on wishlist to now.
Thanks for the tips!!