One of the really interesting things that The Walking Dead has done with its zombies, and was especially noticeable last year, is the way it shows how their bodies are gradually decomposing, and there's a clear distinction between relatively new walkers and those who have been around a long time. That's clearly a ball season 6 is taking and running with, and director/executive-producer/special-effects-guru Greg Nicotero has said they'll be pushing decomposition further this year. That's good news for the show as it helps to keep the walkers interesting and suitably scary looking, and also makes sense within the narrative. It's only natural that the bodies would rot away the longer they 'live'. It'll be intriguing to see just how much of an impact this has on them, and whether they'll remain a big threat.