You asked for advice, here are my comments.  

First, if your product is for Poser, use reasonable shaders. Bagginsbill posted a leather shader, and there are reasonable metal shaders from him and Snarlygibbly around. If you want to sell your product, make sure that every part looks right. All shaders mentioned here are free to use in commercial products IIRC, but it does not hurt to ask the creator first if you don't find a clear statement.

The helmet itself is too glossy, and needs some scratches or dents to look believable. This isn't glossy car paint on these helmets, just a texture won't look right. Up to now that looks like a Poser 4 product, to be honest. 

Helmets are there for protection. You need to see the thickness of the material, and since it's steel, the edges should be beveled. This thing looks too thin, you need a visible rim. Not overdone, though. 

One thing which isn't visible so far - is the helmet conformig or will the straps go right through the neck if the head bends forward? How do you handle that? 

Besides I wonder how many people may buy a helmet alone, without the clothes. 

These are my thoughts to that. What you have looks very good so far, especially the straps are very well done. I hope I don't sound impolite, my posting is not meant that way. 

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.