Yes, we have just started a Deadlands campaign, and I am looking forward to the first time the players meet zombies - they are in for a surprise.
As noted, the Zombicide Undead or Alive game has some nice ones - and some fun Western "survivor" miniatures as well, but there are a limited number of poses, repeated for the zombies.
There are some zombies (four poses) in the Shadows of Brimstone core set. The reworked one for the revised version of the game are much improved. Not a good investment if you are only after the zombies, but you can find some on eBay. Search for "Hungry Dead". Being plastic, they are easy to modify as well. There are I think four different poses, three male, one female.
-Michael