17. The Decaying Titles
One of the really clever ways the producers of the show have visually represented the passing of time is with the walkers, who have been gradually becoming more and more decayed over the years, a sign that this has been taking place for a while.
It's not just the walkers they've done this with though, as the titles have also been slowly decaying as well. That continued in Season 6, with the 'W' in particular more bloodied and rotten than in previous years. Like with the decaying walkers, it's a nice visual representation of time and the world going to hell. Maybe by Season 12 it'll just a black screen.