Expanding on my post about veterans I still haven't figured out what sort of Fluff I want my army to be. They are already pretty diverse enough to be a standard combat company/regiment. A few models have been painted in the normal Cadian Scheme but I was thinking of different schemes which would make them more unique.
I want to make a 2 tone Guard scheme using black for armor and grey for the clothing. Skin tone will vary and misc pieces will be uniform with the company/regiment. Aquila's and other symbols will be done in either a silver or gold. Weapons will be mainly black with the details a bolt gun metal color. This color will work for any the planned fluff I have in development.
Now for Fluff of the company/Regiment I wanted to do either a Naval theme, City Fight/Planet Strike, or Special Forces.
The Naval Theme is easy. The Company/Regiment is on board auxiliary infantry used for repelling boardings and carrying out boardings themselves, they are used for on planet escort duty of high ranking officials and ship high command. If things get too rough they can be loaned to local PDF forces or take part in planet sieges. Members of the company/regiment are not raised from among different planets, they are taken from ship crew members who have a talent for combat, various destroyed regiments and other smaller units that get assimilated into the company/regiment.
Modeling wise, they would be armed with shotguns so veterans would be common, lascarbines for close quarter combat maneuvers, and flamers to clear narrow hallways with out destroying the interior of the vessel. Obviously plasma and melta weapons wont be used too much as no ships master wants a bunch of grunts punching holes in his ship. For obvious reasons there cant be tanks in a ship so any fluff regarding them would be based with "On World" activities. I would use Valkyries and other deep strike abilities as desired as well.
I could write some fiction based off of them, the type of stories would be like reading battle reports from a third person perspective or the commentary of the ships master at arms reviewing combat reports.
The special forces using the same color scheme would be sort of a "They don't exist" type of regiment, Top Level clearance sort of stuff. They would have no unit markings just the standard issue equipment. Heavy use of veteran themes and storm troopers. Make use of some commissars for theatrics and have them be a Black Ship detachment which could make good use of some Psycher battle squads.
Modeling would be easy, standard models in dark and oppressing scheme with standard gear with some kit bashing thrown in to give some individuality to its members but at the same time still capturing the "Men in Black" attitude of the force. They could support any matter of troops and vehicle choices.
Fiction could be written in first person or even third person with the target being a squad or platoon or one of its snipers going in and taking care of its black bagging missions.
Its a toss up between the Special Forces and the Naval theme.
I have a ton of old school guard models laying around I can build a whole other smaller army around 500-1000 points worth made up of the old metal Cadians, a Catachan platoon, Steel legion and the very old school stormtroopers with the berets.