The "look" of Dark Ages is inspired by much of the work of the late, great Ray Harryhausen. Almost all of the Sinbad movies are apt (but especially The Seventh Voyage of Sinbad), as are Jason and the Argonauts and The Clash of the Titans. The particular Dark Ages feel is most directly inspired by Dragonslayer, but there is a good deal owed both to The Lion in Winter and The Name of the Rose. The fantastic A&E version of Ivanhoe might also be most helpful viewing, as is the Brother Cadfael series featuring Derek Jacobi (for the record, this DM considers Sean Pertwee to have been the most ideal representation of Hugh Berengar in the series, which had two other actors in the role).
But how could we not mention Conan the Barbarian, produced by the great Dino De Laurentiis? Enough said. Well, no, not enough. Arnold, yes. But James Earl Jones. Max von Sydow. Now enough.
For more modern points of reference, there is probably little need to mention Game of Thrones. But the inspiration on Dark Ages here is selective-Peter Dinklage's performance as Tyrion Lannister, Jerome Flynn's performance as Bronn, and the entire feel of the Night's Watch. The Wall may come to mind when PCs come upon the Great Wall of Severus, separating northern from southern Albion. But the truth is that George R. R. Martin's Wall is really just another version of Hadrian's Wall (called the Great Wall of Severus in Dark Ages). The more immediate inspiration in terms of the look and feel of the wall in Dark Ages come from two films-Anton Fuqua's King Arthur and Dino De Laurentiis' The Last Legion.
What else? One could mention Harry Potter, but what need? Harry Potter is so central to any DM's ideas of a fantasy universe that it would be redundant to mention it. But Harry Potter must be mentioned, especially in its more Gothic sets, in Alan Rickman's (like Jeremy Brett, taken much too early) wonderful performance as Snape, Dame Maggie Smith's equally wonderful performance as McGonagall, and the ever-talented David Thewlis as Lupin, David Bradley's creepy take on Argus Filch, the forests and pubs, the goblins of Gringott's, the alternating claustrophobia and wonderous variety of Diagon Alley.
Recent film and television that have contributed to my vision of Dark Ages included The Eagle (directed by Kevin Macdonald), Centurion (directed by Neil Marshall), and such series as Vikings, Norsemen, and the various series made of Bernard Cornwell's novels. It would be foolish of me to say that films like Erik the Viking and Monty Python and the Holy Grail haven't been important as well!
The latest shaping influence has been The Witcher!