My finished techmarine (from a Forgefather). I carved the Mechanicus cogs from a shoulder pad and glued them to a shin (the original model has none since I think it predates the mechanicum stamping everything). The iron hands icons were all carved off and replaced with fists. I'm not sure what that weapon is but since it isn't plasma or grav I painted it purple :) I was super worried I'd break the servo arm so I added a magnet where it joins the carapace so that it will bend and snap off instead of breaking. The heavy armour should satisfy the 'artificer armour' requirement of a techmarine.