The flag file for Germany is saved in [gamefolder]\gfx\flags, as GER.tga, replacing it should change the image, the resolution is 93*64. You can use GiMP to do this: answers.yahoo.com/question/index?qid=20080202083800AA59lgm
The flag is probably de-nazified due to some countries having laws against such symbols. I might make a mod of this later.
I guess besides of the flag, you'll also need the pictures of the man with the funny mustache and his friends Simply download the Demo and get the germany.txt file from common\countries folder (for the right names of them) and the gfx\pictures\portraits folder for the portraits. copy and paste and voilá -- uncensored