Hi all,
I am sending out a new message, since I feel this issue is pretty important and impacts a lot of Wikipedia projects. The other issues that Bas addressed also need follow up, but let's tackle these categories first.

This is the list of categories as they stand today on Commons in the top level category (see the email from Bas):
Category:Cultural heritage monuments in Andorra with known IDs
Category:Cultural heritage monuments in Austria with known IDs
Category:Onroerend erfgoed with known IDs
Category:Cultural heritage monuments in Brussels with known IDs
Category:Cultural heritage monuments in Estonia (with known IDs)
Category:Cultural heritage monuments in Hesse with known ID
Category:Rijksmonumenten with known IDs
Category:Cultural heritage monuments in Portugal with known IDs
Category:Cultural heritage monuments in Romania with known IDs
Category:Cultural heritage monuments in Spain with known IDs
Category:Cultural heritage monuments in Wallonia with known IDs

I think only the Belgians and the Dutch have chosen their names well, because they are using the terms that are covered by law in their country. The other categories should be renamed to reflect the legal term in those countries. My reasons are as follows:
1) The term "Cultural heritage monument" is not defined anywhere, in any country's wikipedia.
2) We are using a formal designation that has been assigned by a government agency and is covered by the European Council's international law on cultural property. In order to refer to the proper designation, we need the formal name of the designation.
3) The sub categories are going to have native names anyway, so why have a strangely named top-level category that no one understands (including English-speakers)?
4) When we make interwiki links to these things we should be consistent across all countries. 

I noticed a confusing situation has already occurred in the German Wikipedia, where the top level category for the Austrian monuments is "Kategorie:Liste (Kulturdenkmale in Österreich)", when I fully expected it to be "Kategorie:Denkmalgeschütztes Objekte". On Commons I would expect "Category:Denkmalgeschütztes Objekte with known IDs", and in the English Wikipedia, I named it "Category:Denkmalgeschütztes Objekte".

Jane