I wasn't going to include Paul Klee until I told a couple people about this post (a rarity before posting). I was informed that Klee was no more well known by the general public than the others.
I confess that I am not familiar with Christoph Kiefhaber and that I have only a passing recollection of Heinrich Campendonk. A deficiency in knowledge on German-speaking painters that must be corrected.
Other artists here include Alexej von Jawlensky and Kees Van Dongen.
Click on the artist names (just in case you couldn't figure this out) to find out more on each artist. All the links are to a variety of sources that I thought were good ones on each artist.