Steam Jetpacks: You said it yourself they aren't realistic and my fantasy world aims to be realistic.
Air Ships: Their wouldn't be many as their only cities are in amazingly windy areas but they would be great to add.
Tanks: Probably not as they don't really fit the theme. Only the gnomes will have steam punk gear and the rest of the world would have to use medieval and magic or buy it for Aquitean Caravans.