There is some great poster art from the period.
I have the two following books, which I heartedly recommend, if further interested in the subject.
'Propaganda - The Art Of Persuasion: World War II' by Anthony Rhodes. 320 pages (this one is about both Alled and Axis propaganda)
'Kunst Und Propaganda in Der Wehrmacht - Gemälde und Grafiken aus dem Russlandkrieg' by Veit Veltzke. 255 pages.