Some words from Jalf Flach ( http://www.rondom1900.nl/ ) to this image:

In my modest opinion it is fore all, a Neo Classical building, but the
angels are definitedly Art Nouveau inspired.
Anywhere else in Europe everyone was bored with the so called neo styles,
(neoclassical, neo gothic etc.) around the 1900 hundreds, but it is my
experience that in Vienna and München as well (AND in Italy, but that was
the cradle room of 'Classic') there was not such a crack between them.
Classic, neo or not, appeals to a sense of beauty of many people.
Even Victor Horta at the end of his live designed again buildings in a
classsical style.
Art Nouveau trigered that; because many people got bored of the
superabundant decorations of it.
So I think, this building is having the best of both worlds.