Pittsburgh Steelers
1954 Bowman card
1958 Topps card
The 2 right cards must have been taken pre-1954, as the Steelers had added the black stripe (like the 1958 card) by 1954.
1955 Topps card
c. 1961 vs the Niners
Bobby Layne 1960
1962 "Steel" version
More 1962 yellow helmets with "Steel" logo. Bobby Layne to the left an unidentified lineman to the right. Thanks to Kurt Sanger for providing these images.
Lou's 1963 Topps card
Unexplainable photo from the Pro Football Hall of Fame. This is supposedly a helmet worn by Lou Michaels in 1962 or 1963. I've never seen a game picture or a Steeler helmet with the logo on the left side???? 
Also from Canton - this is the helmet worn by Bobby Layne in his last game as a Steeler. This game was the "Playoff Bowl" against the Lions in January of 1963.  This was the first time the Steelers wore a black helmet. Suprisingly, the logo says "Steelers" and not "Steel". This image and the Lou Michaels helmet above are courtesy of the Pro Football Hall Of Fame.
Rocky Bleier custom reproduction by Helmethut
Mid 70's: Bradshaw w/his Dunguard mask
Current Steelers Helmet
The 1994 Special Throwback
John Henry Johnson "wide stripe variation"
Helmet Hut reproduction