No, you are basically right there Chaosftw. The only thing that really sets these guys apart from other armies, is the magnetising... and that isn't really something you can tell (or shouldn't be, if you done it properly) when you look at the miniatures.
That's the main problem with the GK imo. It's not exactly a converter/modellers wet dream. GW did a great job on the plastic kits because they are so complete... There isn't a weapon option/upgrade/whatever that's not provided within the plastic box. The only thing you sort of have to work on, is the vehicles... If you don't convert them slightly or add a bunch of iconography on them, they'll just end up being silver marine vehicles. Or you could go the easy way and fork over the cash for the FW bits. My third dread is going to be a spruced up venerable DN however.
And colorscheme wise, it's a bit of a "boring army" as well... It's a single chapter with no succesors whatsoever. That doesn't really leave a whole lot of elbowroom in terms of creativity to begin with.
I have seen some really cool black GK armies in the project logs, but that's not really my cup of tea tbh. I'm more of a traditionalist. But luckily, I find the red/white/gold/silver/black scheme very striking and nice (that's also the reason why my old inducted guardsmen are painted in those colors).
But don't worry, I'll be working with GS soon to make cloaked backpack (to represent purifiers). But first, I'm going to have to hammer these basic troops home. I despise unpainted miniatures on the table! As soon as those core units are done, I can get on to the more "juicy" stuff like the henchman units. Those really are a modeller's wet dream.