Re: Art movements
Contrary to the Hudson River School, the Dusseldorf School doesn't seem to have a real unity.
I thought a little bit about this and i think you are right that its not a homogenous, narrow body as the Nazarene or the Hudson River School. It was famous for it exquisite and detail drawings and finished paintings. But it is not only landscape painting. History (not the idealistic, classical style) or social genre are very important too.
The Dusseldorfer School is more like a trademark, as the École des Beaux-Arts in Paris.
A good overview you can find at <a href="http://www.kettererkunst.com/dict/painting-school-of-dusseldorf.shtml">Kettler</a>
Maybe we need not only the movement-selection, but also a marker for these schools. In germany the Weimar School, the Munich(Piloty)-School, the Berlin School, the Dusseldorfer School and so on.
Another thing that would be useful in my opinion, are categories for the typical kind of pictures an artist made. If he is mainly a landscape-, history- or portrait painter for example.