Beast races have come a long way. In morrowind you were lucky to find a helmet to fit your character, unfortunately it was impossible to ever find shoes due to the size of the race's feet. In oblvion this was fixed and anything could be worn by each respective race...I believe this was explained lorewise by saying you were now playing as a different subset of your race, which happened to have more of a human shape. This was pretty cool except for the fact that argonians didn't really look that lizard like now they had more of toad/turtle looking face, and it was impossible to get a neat looking complexion that matched the rest of your body (mainly because the creation process was pretty horrible...move one notch and the rest went everywhere). Now in Skyrim Argonian look like savage raptors, I'm really happy with the way they look, and I can still wear anything I want, but here's the problem. Even though every single piece of armor is available to my character, it doesn't really look all that great to wear them. For example look at dwarven helmet, the imperial closed helm, and dawnguard heavy helmet...these are without a doubt some of the coolest looking helmets in the game, but I'll never wear them because it obviouly wasn't designed to be worn by an argonian...it lookis incredibly unappealing having a blunt flat faced helm with a tail sticking out of your character.
My hope is that in future, when you put on a closed faced helm it will be elongated if your playing as a beast race, and if you put on a chest piece, armor will be placed on your tail of the same matierial. To get a mental picutre of what I'm trying to explain google image search "BANGA DRAGOON."
(I WOULD POST A LINK BUT IT DOESN'T LET ME AS I JUST JOINED THESE FORUMS; SORRY!"