The Decaying Dead
We are roughly 900 days into the apocalypse at this point (the end of season 7). In those 2.5 ish years, the walkers have decayed significantly.
In season 1, walkers look human. Humans on a bad day, but human. They have all their facial parts, the clothes are mostly intact. They have glimpses of humanity.
Little Girl Zombie
Jenny Jones Walker
There is more disintegration of the skin and eyes. The skin is discolored and decaying. Most walkers do not have lips at this point.
Clothes are rotted. The disintegrating bodies are more prone to becoming incapacitated by less force including high pressure water and falls. Noses are sometimes missing. Hair has fallen out. More trauma to the body.
Get Off the Road Walkers
Fire Hose Walkers
Walkers condition is truly dependent of their environment. They are either bloated corpses from the water or bleached from the sun. We see many more rotted with exposed organs walkers.