Railway locomotive boilers were pretty much constrained to width and length due to clearances, but there were some differences on fireboxes as technology moved forward.
Combustion chambers became popular on medium and larger locomotives where higher steam generation rates were needed to keep up with increasing speeds.
Superheating was the biggest steam advance I believe, followed by feedwater heating, higher pressures and combustion chambers. These certainly are not all of the advances made to the industry though.