The official regiment for him was the standing Planetary Defense Force of Fortis Binary. His fatigues are leftovers from his old standard-issue PDF gear and his outer jacket is made from a heavy all-weather fabric and worn to help deal with temperature and environmental changes, both naturally-occurring or accidentally self-induced. The rubberized vest underneath his jacket is cut down from a full CBRNe/hazmat protective suit which would have been worn by one of the regular manufactorum workers of Fortis Binary before the planet fell to Chaos, but is worn by this psyker now more as a barrier to any incidental contact with contaminants or biological/mutagenic poisons in the course of combat amongst the factory and munitorium ruins.Although this Renegade Psyker is intended to be a member of The Shriven, and my background and theme is in part based from Dan Abnett's "First and Only" novel, for everything else I'm more or less making things up as I go along. I'm somewhat in the same boat as Dave Taylor with his Blood Pact army in-progress; only not nearly as talented, artistically inspirational, well-known, or in the market for a new tattoo. Okay, I'm nowhere near in the same boat as Dave Taylor, but I'm basing my force on something Dan Abnett came up with that was inspirational enough to form a tabletop army around, except I'm lacking in the finer precise details like "official insignia," "color scheme," and "general appearance" (see below the "Dave's Got Ink" heading on the above link).
Oh, and I'm not actually griping about the lack of particulars for The Shriven, really; I guess it's a credit to Mr. Abnett that he's talented enough to get me buying more of his novels as I find them simply based on his authorship, and also keeping a steady flow of cash into Games Workshop's coffers on impulse purchases of tiny plastic and resin miniatures - it's my own damn fault, and I'm enjoying myself!
As to the Renegade Psyker himself, I was able to get some painting done last night and finally settled on a spot color for this guy, if not the rest of my eventual Shriven force: