Ticked off that you're stuck in the boring blue power-armour of a boring blue Ultramarine in Warhammer 40,000: Space Marine's singleplayer campaign? While you can't stop Captain Titus from banging on about his Chapter, thanks to one modder's hard work you can now make him look like he belongs to another, less vanilla entry in the Codex Astartes. Newly added to the mod, at last, are helmets - so you can look like a proper Space Marine, not the 40K equivalent of that bloody Stallone Judge Dredd movie.
Grab the skin/chapter/head redesign of your choice from here - or indeed skins, as you can have as many installed as you like, each Chapter having its own launch shortcut. See each mod's readme file for installation details and whatnot. By default, the mods are designed for the demo, but just remove the word 'demo' and in the file properties/path of the new shortcut and it'll work with the full game too.
However, multiplayer appears to be deactivated while the mod is running. Which isn't much of a problem, given you're running it to play singleplayer, right?
Now, if you'll excuse me, I'm off to be a Dark Angel. I love a bit of dark green, me.