It used to be books, I am, or more accurately was, a voracious reader and since I’d read a significant amount of literature set in the games that I wanted to run or play in then I could use that to my own ends. That’s changed though, I have significantly less free time and so when I’m running a game virtually all of my reading time is usually devoted to the rules and adventure, as opposed to wider reading. I still use books as inspiration and I still recommend certain novels to people who want to play certain games, 2XS and House of the Sun for Shadowrun, The Chronicles and Legends for Dragonlance, At the Mountains of Madness and The Dunwich Horror for Cthulhu and many others.
For me, nowadays, it’s TV, far more than even movies (though I saw a whole lot of Numenera in Guardians of the Galaxy). TV has advanced to such a state that it’s held almost in the same regard as film, actors don’t see it as a step down if the show is right (say like True Detective) and networks pump massive amounts of money into shows with Game of Thrones reportedly costing $6 million per episode and Walking Dead around $3 million. Plus, with the rise of traditionally fantasy and sci fi genres in the mainstream, like the aforementioned Game of Thrones and Walking Dead, plus the surge in popularity of Comic Book movies, more subjects that would traditionally be too niche for the mass market are being greenlit.
This means I can find great, hard edged sci fi, like in The Expanse, or fantasy like Shannara or Game of Thrones, it means that I can see settings and themes I love treated seriously and with respect and that helps me form ideas in my head how I want to run games or what kind of character I want to play. If I want to understand how close nit a criminal organisation might be then shows like The Sopranos can help me, if I want to understand gangs then Sons of Anarchy, the Shield and the Wire all give me different perspectives on different types. If I want source material for Deadlands then I need look no further than H*** on Wheels or Deadwood.
I’ve even found inspiration for games like Call of Cthulhu in TV shows recently, with Season 1 of True Detective essentially being about a worshiper of Hastur and with more supernatural shows like Sleepy Hollow essentially being a mash up between Cthulhu NOW and he forthcoming Pulp Cthulhu. H***, Hunter the Vigil is literally embodied in the TV show Supernatural in everything except name and all this is before I start looking into lower budget shows like Dark Matter and Killjoys that make perfect inspiration for Traveller, Firefly (which has its own show anyway) or anything in a space operah setting.
Inspiration for RPGs can come from anywhere but, today, I find it most prevalent in TV as the world embraces geekdom, as ComiCon becomes a mass market spectacle and people tune in every week to find out what an orphaned girl with 3 pet dragons might do next.