According to Terry Spacemasters Imperium was based on Dune.
I think the idea of galactic monarchy is pretty common in sci-fi. You have it in the writings of Asimov, Niven, George Lucas, and Frank Herbert to name a few. It's also the basis for Traveller's Third Imperium setting as well as the Warhammer 40k human space setting.
If we get out of the solar system, and scientifically that is a very big if, I fully expect someday someone will declare themselves 'Emperor of Known Space' at gunpoint.