When I ran Eberron, it was as a magical variant to world war 2. My history degree gets used rather heavily when I run an Eberron game, which I like.
Heh - I ran with it being the equivalent of WWI, with WWII visible on the horizon. It is in some ways very much a 1930s Pulp setting - complete with lost continents and dinosaurs!
The setting is great for espionage and intrigue, I even ran a direct theft of 'Strangers on a Train' as a mystery adventure and 'The Third Man' for an espionage adventure. Another adventure centered around the team, including a Paladin, being hired, through cut outs, by the above mentioned LE Vampire seeking peace' to find an agent that was trying to trigger a war.
I
highly recommend reading Raymond Chandler and mining his stories for ideas, heck, one of the adventures goes so far as to paraphrase his line 'When in doubt, have a man come through a door with a gun in his hand.'
Dashiell Hammett is another excellent source, going for a noir and pulp tone. The Continental Op in particular, for a more intrigue and espionage flavored game, without dabbling your toes into the James Bond -
Mary Sue Super Spy genre.
Good people can perform some of the nastiest acts with the best of intentions, be it in the name of gods or for love of king and country. Sometimes there is a good reason why the victim of a horrible murder was killed. And sometimes, they were just in the way.
The setting assumes that if magic is as common as it typically is in D&D then it will be used to solve some of the same problems that were solved by technology in our own world - the train, the
zeppelin airship, rapid communication and the attending commerce.
Trips into the Mournlands can be pretty damned grim, especially for those who came from Cyre, a bit like how a post apocalyptic setting might feel to the survivors, seeing a recognizable landmark torn apart and changed by whatever fell energies destroyed that nation....
The Auld Grump, He snorted and hit me in the solar plexus.
I bent over and took hold of the room with both hands and spun it. When I had it nicely spinning I gave it a full swing and hit myself on the back of the head with the floor.