The Metropolitan Museum returns a relatively poor showing again this year with just five Advent calendars, despite a dedicated catalog section for the same. The avian calendar is the most worthwhile; old customers will miss the New York-themed calendars. The three-dimensional tree-calendar option is gimmicky.
The (US) National Gallery has a varied selection of fourteen calendars. The official 2018 calendar ($14.95) is religious, while the others are merely about Christmas. (The Norman Rockwell one looks like fun.)
The (UK) National Gallery does a somewhat better job again this year, especially with its ongoing offering of the very wonderful altarpieces calendar.
Top prize for good calendars this year goes again to the Fitzwilliam Museum at Cambridge, whose eight offerings cover themes religious, Japanese, and medieval. All are priced under £3.