You can download a pdf of the Albatross steam flyer shown above.
One of those great ideas that never was is the mole machine — a transport with a giant drill on the front that carries troops under enemy lines.
Here are some instructions for building one for your 28mm troops.
For the Victorian Science Fiction / VSF / Steampunk Fans:
Phillip Fickling has a paper model of a submarine that may be of use for victorian science fiction fans. Click on the free model link.