Suggestion

I don't have any drawing or photoshop skills, so I'll only able to give ideas:

1. I found at my university's library a book called "Art of the Third reich", by Peter Adam, apparently based on a TV series of 1988 for BBC. This book is full of images of art and propaganda of Nazi Germany and provides insight on these subjects. I really think that anyone designing posters will find this useful. See if you can find it in a local library.
http://www.amazon.com/Art-3rd-Reich-Peter-Adam/dp/0810926156
(not saying to buy it, only for show)

2. Real life material for inspiration:
http://fcit.usf.edu/HOLOCAUST/ARTS/ARTPROP.HTM
http://www.calvin.edu/academic/cas/gpa/sturm28.htm
http://www.calvin.edu/academic/cas/gpa/brenn1.htm
http://www.calvin.edu/academic/cas/gpa/lehmann.htm
http://www.calvin.edu/academic/cas/gpa/ww2era.htm#Posters
http://www.earthstation1.com/German_Propaganda_Posters.html
http://www.third-reich-books.com/third-reich-nazi-posters-art.htm

3. A poster highlithing a strong, powerful, blond, german soldier, looking ahead, as if seeing a glorious future. They don't have armored forces and aircraft anymore, so their most valuable resource is the limited number of soldiers and support personnel in the base, and those must be emphatized, instead of machinery (maybe except for the saucers). The poster could also name them the members of "Werwolf", the underground resistance movement that keeps fighting for the german ideal.
http://en.wikipedia.org/wiki/Werwolf