The item being modelled in this picture is a rapid-fire battle cannon. It's basically a big lump of machinery with a shield and a barrel. To make it more interesting, I've added a sort of barber's pole decoration to the barrel (done with a spray can and the sticky strip cut from a post-it note) that hopefully looks a bit like a medieval lance.
Here we see the big machine gun, which is a mega gatling cannon or something like that. I added some bluing to the end of the gun, which seems to have come out bizarrely pretty.
Also, the battle cannon fits conveniently on a small wooden cart, in the event that I take up Napoleonics in a hurry and have to improvise a wheeled gun.
Being unable to resist the urge to muck about with the original kit, I decided to add a pilot. I happened to have a model lying around from a failed attempt to build an LRDG-type buggy from an ork truck, and I removed the steering wheel and added some extra bits. To be honest, I expect that the driver would be wired into the machine by a neural link, but what the heck, he's got a gearstick instead.
The next step will be to finish the rider and paint/assemble the body. I'm not looking forward to painting the canopy, especially as I don't have an airbrush. And after that, it'll be time to put on all the fiddly bits.