I've seen a few different variations of Imperial Legion armour in the game, excluding the light/ medium/ heavy sets that you can get for signing up. I talk of the Officer Helmet and the 'Imperial Helmet', which I found during the Thieves Guild story line.

Are there different whole SETS of armour, or just these helmets? I'd like to know, because a full plate armour that matches the Imperial Helmet would look AMAZING.

http://images4.wikia.nocookie.net/__cb20120421225622/elderscrolls/ru/images/1/10/ImperialHelmetAlternIconSkyrim.png

http://images1.wikia.nocookie.net/__cb20120612172736/elderscrolls/images/d/df/Imperial_Helmet_Officer.png

They both match the heavy armor set, but not the craftable version of the boots and gauntlets