Next I hit on the idea of making them an Iron Hands successor chapter with added steampunky goodness. It went astray a bit?
I ended up with my basic Protector Maniple. Fluff-wise these are heavily armoured warriors created by the Adeptus Mechanicus of Demiterra Nemusordo. They're controlled by servitor brains but are largely robotic not organic. In game terms, these are my Tactical Squads / Grey Hunters / Plague Marines / Thousand Sons.
Some steps in the creation of models for this army. As you can see, the torsoes are plastic Space Marines- I've got a mix of multipart ones and ones from boxed game sets (Space Crusade, 40k 2nd Ed, Assault on Black Reach). They have their legs and heads removed, and the chests filed smooth. The shoulder pads are filed smooth and then have greenstuff Adeptus Mechanicus symbols added, as are their backs. The lower half is made from three bits of wire plus a load of modelling putty. Finally the necks are plastic tube and the heads are Westwind Productions WW2 gasmasked heads, cut in half to just leave the odd helmet and the huge lenses.
Painting is fairly basic. Black spray undercoat. Robes are Blood Red, metal is Boltgun Metal, details are Skull White or Dwarf Bronze. Everything is washed with Badab Black, then neatened up a bit. Finally eyes, power weapons etc are Scorpion Green over Skull White.
A whole lot of Protectors in various stages of completion! The painted squad and the back two rows are Protector Maniples (Tactical-equivalents), the squads in the front are Protector Support Maniples (Devastator-equivalents). You can also just about make out a standard IG Techpriest Engineseer, there to be a Techpriest-equivalent.