Chrome letters are nice. I just passed 400,000km and I like Ruking's idea.
Pizzaman sells chrome emblems to match VW:
http://needasticker.com/custom-emblems.htm
Here is another example of the matching emblems Pizzaman sells:
http://forums.tdiclub.com/showthread.php?t=239186&page=4
The way I celebrated when I hit 400,000km (248548 mi) was to replace the shocks and struts, replace front and rear brake pads, replace glove box, replace timing belt, and change the oil, which took up about 5 weekends between 396k km and 404 k km.
(did all of the work my self except for help with timing belt)
Congrats!
p.s. also 4 new tires.
And washed her outside and vacuumed her inside.
p.p.s also replaced VNT actuator.
Should be good for another 160,000km (100km mi)
Like oilhammer said, celebrate by driving another 200,000 mi.
I plan on celebrating at 500,000km (half milllion km) by either buying a new car (Mazda2 or Honda Fit at the top of my list right now) or by buying another timing belt kit for the Golf in preparation for 556,000 when she is due for her next timing belt!
Congratulations on 200k mi.