So here are some of my recent customizing efforts.
This is my new Belgian combat walker, complete with belly-mounted three-inch gun. It began life as a science fiction robot tank but had enough clunky detail it was easy to convert into a steampunk vehicle. All I really added was the gun, the hatch and commander, smoke stack, and a couple brass pipes. The rest is the original model, although painted to emphasize the pistons and gears. In painting these I try to keep a dark look and use the brass sparingly, to highlight or accent certain details. I've added a picture of the pre-conversion model immediately below. As you can see I really didn't do a whole lot, but it has an almost completely different look and feel now.
Here are two views of my new Auto-Mitrailleuse Blinde Legere Modelle 1887. This model began life as a horse-drawn fire engine. I added the armored compartment in front as well as the crew, and scratch built the mitrailleuse (not hard at all). Leaving it open-topped and adding the visible French crew helped the look a lot. The officer is a British naval officer from the original Space: 1889 Adventurers set, painted as a French officer. The forage cap makes a pretty good kepi. It's also the same figure I used as the commander of the Belgian walker above. (I have a bunch of these and you can only use so many naval officers.) The French standard bearer in the picture below (Liberty leading the masses to freedom) is courtesy of Tom Harris.
This is a less lethal vehicle: a steam tractor being used as a prime mover for a field gun. This was one of those plastic toy vehicles for one of the steampunk movies which came and went a couple years ago. The vehicle had a cab and engine -- basically what you see here -- attached to a big wooden keg trailer which opened up to show a rocket launcher. I didn't care for the trailer much but the tractor part was very nice so I cut it free and used it as a separate vehicle. I added the smokestack, some piping, and the driver (apparently from the Quartermaster Corps) but aside from that all I added was paint. I went for a two-tone white-over-black paint scheme inspired by the way a lot of battleships were painted back then.
This truck started life as a vehicle from the same movie (I think). It had a guy who popped out of a rear hatch and said "Boom!". I disabled the cute sound effects, added a smokestack, some piping, and a driver, and voila: a Heavy Steam Lorry. Just the thing for hauling supplies deep into the Martian interior, or hauling treasure out.
Last but by no means least we have a mad scientist and his gaggle of clockwork spiders. (Do clockwork spiders come in gaggles? I guess they do.) I was looking for something to use as the basis for a small clockwork spider at a game show and in one of the booths a guy had a bin of these little saucer-shaped spaceships -- I think they may be Cylon fighters -- for a quarter apiece. I grabbed a handful, added legs from fine wire, a little paint, and here you go.
I really like these a lot. I'm not sure they will be all that effective in a game (unless you judge effect by comic relief), but I've discovered that the things I lavish the most effort on are usually far less dangerous than just some big ol' tank.
I like imagining things with my hands. It's a good complement to writing. Sometimes coming at an imaginary world from a different angle than words can make the words come easier later.
Or if not, it's at least fun.