The key shrine=* is used in Poland to tag a Roman Catholic church or other sacred place which is "visited by the faithful as pilgrims. For a shrine to be described as national, the approval of the Episcopal Conference is necessary. For it to be described as international, the approval of the Holy See [the Vatican] is required"
It has also been used a few times in other countries to describe other kinds of shrines, such as historic=wayside_shrine.
How to map
Addition to tag amenity=place_of_worship
Values in use