I took a pic of the Park Avenue on Thanksgiving Day 2012, when it achieved 100,000 miles. Now, of course, I can't find the pic.
The W126 Mercedes never got to 200K miles, as it was totalled about 1500 miles before that. And I bought it at 135K, so I never saw the 100K mark. I did go to the dealer and get the high mileage badge the Merc qualified for, the 250,000 km mark (155K miles), and fastened it on the grille.
So I guess I would celebrate or mark a mileage milestone with my car, if said milestone happens while I own the car.