Personally, I think Conan the Barbarian got it wrong. Crushing your enemies and all that is pretty good, but making little space people out of increasingly unlikely old miniatures is way better. I've been back at the Stargrave people, enjoying sticking new heads and arms onto historical miniatures.
Here are a couple of space adventurers. The woman on the left has a Bolt Action Russian body, with Stargrave head and arms. I reckon she's some kind of well-off rebel. The lady on the right is a standard Stargrave plastic model. She's a dodgy corporate bureaucrat, together with jolly company hat.
And now for something weirder.
The rest of these guys were made from old plastic English Civil War infantry. I think they might be Perry models; they're pretty ancient and weren't doing anything useful in my cupboard. So... they became space people. I removed the heads, and left off the arms.
Here they are painted.
The man on the left is based on a musketeer. I gave him a Stargrave head and arms from a Wargames Atlantic Grognard space soldier. They both looked quite old-fashioned and military, which suits the marching pose of the body. I painted him to look neat. I think he's either the crew of a spaceship or perhaps the leader of a militia.
The chap on the right was based on a pikeman. He's got a Wargames Atlantic face and helmet, and Stargrave arms. He looks as if he's stopping a citizen. "Please stand still while I scan you for witchcraft".
And here are the other two.
These guys were also based on pikemen. I noticed that all the base models were facing the same way (which makes sense in a pike regiment), so I gave this chap a left-handed gun to "turn" the model to the left. I also cut his lower left leg and turned it slightly, for a more forward-facing pose. Lots of bits were added to his waist to break up his Civil War shape. His head has goggles and bandages, rather like the invisible man. He was painted to look like a grotty bandit, with a fairly drab colour scheme that reminds me slightly of the Afrika Korps. To make him more sci-fi and visually interesting, I painted his lenses red.
The final weirdo has a head and arms from the Stargrave female crew sprue. When I sprayed the model black, the outline and pose reminded me of a ninja. So, she got a black paint job. The eye-slit in her helmet stresses this. I really like her shape: she's got an aggressive feel, as if about to kick down a door.
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Everything I've Learned About Converting Historical Models Into Space People
By and large, I reckon that most historical miniatures could be converted into space people. For one thing, science fiction covers a lot of bases, from the near-future of cyberpunk to the wild designs of Moebius, and artists like John Blanche often riff off real historical costumes anyhow. You might have difficulty where a model is wearing a very recognisable garment, or where the body isn't properly covered. It's going to be difficult to explain why someone is running around in space dressed in flip flops and a kimono. Perhaps they're some kind of deadly monk who swears off other kit. Or a psychic who can conjure their own protection. Or just a non-combatant. You just need to make them look like that.
Heads
First up, I'd suggest keeping some female heads. For one thing, you might decide that someone in armour is a woman, so you need a head for that. Also, a lot of historical/real world models are slighter and a bit smaller than SFF models, so it would make sense to use female heads for them. I've found that female heads work really well with Bolt Action bodies. When covered in armour and gear, it's likely that a fair number of women would look a lot like slightly smaller men.
Also, head swaps can really improve a mediocre model. I don't think that the Bolt Action Soviets are particularly great miniatures, but the Stargrave heads are newer and better-detailed. The head is often the first place you look when looking at a miniature, so it helps a not-brilliant body greatly if the head is good.
Shapes and Silhouettes
Converting a model isn't a matter of where the model/piece came from, but what it looks like. A gun barrel could become an exhaust pipe, a club or even a walking stick. It's a matter of turning the piece around and thinking "What can I use this for?".
When using bodies from other ranges, it helps to look at the overall silhouette of the model and play to it or disguise it as necessary. The main things about the English Civil War infantry are: (i) the long jackets, with visible collars; (ii) the trousers, which are very baggy up to just below the knee, where they meet the big socks (I'm pretty sure these are not the technical terms); and (iii) the belts and bags slung across the body.
With these models, I wanted to hide some of the stuff slung across their chests, especially the "apostles", the little wooden cartridges that musketeers use. (They look a bit like small bottles, and perhaps you could paint them as such). The easy way to do this is to cover them up with arms that hold rifles or shotguns and, if needed, with backpacks. You could cut them off, but then you'd still need to put something over the top.
You can also break up the silhouette by adding new elements, particularly shoulder pads and stuff on their belts. I don't think any real army has ever had big shoulder pads without corresponding armour, but it's a classic science-fiction look. Likewise, adding a load of extra bits and bobs (particularly grenades!) to a model's waist firstly shows that they've got modern tech and breaks up the shape of the original historical model.
Painting the Conversions
Painting these guys is pretty simple: just don't paint them the colours that they would be in real life. For these models, I deliberately avoided red and orange clothes, which were big in the English Civil War (so was blue, but less famously).
When painting, you can use colours to draw the eye to the bits you want to stand out. I didn't want people to look at the lower legs and feet of these models, so I've left them very dark and only vaguely highlighted. You can also disguise the origin of the model by painting historical bits in non-historical colours (so, a metal breastplate might be bright red).
A good trick is to link parts of the model by painting them the same bright colour. On the blue soldier, I've painted both his sash (historical) and his shoulders and cuffs (sci-fi) the same light grey. This helps give the impression that they ought to be together. Likewise the sci-fi helmet and Civil War body armour on the shiny soldier.
And that's pretty much all I know. Thanks for reading this far. Here's the company lady and her android bodyguards. I'm not sure what I'll paint next. We shall see...