Not sure I'd have gotten something else as Diamond. My status changed from Platinum to Diamond while in the air to Bali, and shortly before arriving at the hotel.
So, as a Platinum (that's what it says on the letter) this is what I got.
Written on the mirror
The mirror was a nice touch and unexpected. Makes up for the (generic) printed piece of paper
One thing to add: The welcome drink is from a set list of drinks (house wine, small beer, soft drink, coconut that had ran out). A small beer for Platinum / Diamond is maybe a bit stingy in a country where beer is dirt cheap anyway. In other hotels I've usually always received a large beer, and sometimes even specialty beers even though the voucher normally only covers a regular lager/pilsner. It's not going to spoil my stay, but I did feel a tiny little bit cheated there.