Nice picture. Really looks WWII-inspired.
Seriously, Krieg soldiers look like WWI/WWII Germans IN SPACE.
As it seems to me, all the setting of 40K is basically exaggerated Galactic WWII. Imperium is The Third Reich, Militaristic Japan and Soviet Union AT THE SAME TIME. They worship Emperor like Japanese, xenophobic like Nazi and iron-fisted totalitarians like Soviets.
Both 1984 and WH40K were created in Britain as reflection of real WWII horrors.
And also WH40K can be called anti-religious because nowhere religion is portrayed in such horrible and gruesome way. The Emperor's cult is very close to medieval christianity with knights, crusades, witch hunts, racks and stakes and killing people in the name of God. Chaos religion is just typical "lovecraftian satanism" with tentacles and human sacrifices. Orks are just barbarians. Every images of religion are very unpleasant and covered in blood.
Warhammer 40K is the most gritty fictional universe. And it seems to be more realistic than Star Wars despite this is dark fantasy/lovecraftian horror/space opera hybrid.
It even seems that OUR ACTUAL FUTURE CAN BECOME RATHER SIMILAR!!!