Steampunk basically envisions what would have happened to tech if two things had happened:
1) Limited or non-networked electricity.
2) The absence of solid-state tech (transistors and the like).
Basically, if it's powered and run by non-electric, non-solid state means but does what you'd envision a solid state electrical device to do, it has a good chance of being steampunk.
Read "The Difference Engine", by William Gibson and Bruce Sterling, and "The Diamond Age", by Neal Stephenson, if you want some definitive steampunk fiction.