To me, Steampunk defines a setting in which Engineers are, in a way, gods.
It's a philosophy which breaks with the medieval era of "if it's a heretic, kill it" and moves toward the "why do y, if for the same price we can have this many x?" a certain superstition and tradition has been shed and replaced with rationally trying to solve problems via calculating machines, not the whims of people. If you are doing something with steampunk, don't just slap valves on everything, make it a cultural phenomenon as well, the ire of religious establishment, the industrialization of the farmlands and subsequent movement of under schooled workers moving to the city's, trying to get by. The start of worker unions. Yes, the main attraction to Steampunk is machines, but it's the people that bring it to life.
Btw: I've seen Steamboy come by, Last Exile is also an example.