I like it. It looks like the kind of armour a rebel would wear, being somewhat piecemeal and improvised, whereas the Legion armour with its flowing capes, plate armour, and rich red colouring looks like the kind of armour an imperial army would wear.
It is nice that the Legion armour has several grades of quality, ranging from padded leather armour with no helm, to full plate armour with a helm. I hope this is replicated in game and that there is also grades of quality in the rebel armour (because it would be stupid for the leader of the rebels, Ulfrc Stormcloak, to not be well armed and armoured).
The red/blue contrast is nice, and mirrors the contrast used in the English Civil War, although in that case the 'rebels' (Parliamentarians or roundheads) wore red, whilst the Royalists (or Cavaliers) wore blue. All in all it looks very promising and hopefully it is set up niely for some really good pitched battles between the two sides. I look forward to choosing sides and deciding the destiny of Skyrim!
Spoiler
The Legion armor in game itself looks as it should, with clear Roman influence, similar to Morrowind combined with Oblivion, which makes sense to me, given that the armor worn by troops in Morrowind and Skyrim is that of Frontline soldiers and has to serve both to protect the soldiers, and be a symbol of Imperial Dominance to the local population, their Armor in Skyrim captures this perfectly, much the same way as it did in Morrowind, of course it still retains some of the feel of their armor in Oblivion, especially when you get into the heavier variants, which is really cool....anyway my point is that I agree with your statement but wanted to say that the way it's presented in the concept art isn't much different, and it feels so right. Imperial Armor does have variants, so I'm sure Stormcloak will too, and it's probable that other armor types will as well.
And yes, the contrast between the coloration of Imperial Armor/Uniform and that of the Stormcloak rebels is very fitting, as well as the contrast between the way the armor of each group actually looks.
The Stormcloak armour looks like what it should look like, Nordic and fitting for Rebels, but compared to the rest of the armour, it just feels too...light? I prefer Heavy Armour of course, so hopefully they have some kind of heavy variant for it.
I don't think you'll have anything to worry about,
Spoiler different variants of armor types are present in the game, for example, light and heavy Imperial Armor are present.
, though I don't actually know about Stormcloak armor variants, it's fairly safe to assume the Stormcloak armor will follow the same practice.
Oh and for the record, I think the Stormcloak Armor is pretty damn cool looking and fits the 'persona' of what their group is supposed to be, and if I weren't such a diehard Imperial loyalist I'd be joining them on my first playthrough, I -know- I'm definitely stripping the first Stormcloak soldier I kill. xD