Then there is this funny trick I've learnt: You can actually steal freely from the whole history of the world, and instead of being looked at as a copycat, people think you're really smart and well-educated. Huzzah!
At the moment I'm doing history for my A-levels, and we're learning about the totalitarian states of Nazi-Germany, Fascist-Italy and the Soviet Union. Fittingly enough our story is about two totalitarian states at war.
Another fun thing you can do is mixing time periods together, like we have some technology and style from the 20s, but the also stuff from, say, old Mongolia.
So in the end, history's a nice fellow. Use it well!
Some of my current inspiration:
Europe during WWII
The Mafia in the 20s
The French Revolution