The entire image lacks sharpness and contrast. Maybe try to add in details by hand, and mess around with the color settings a bit. I would up the saturation a tiny bit, add some contrast, and maybe a little brightness too. Just using the sharpen tool/filter isn't going to do the trick, really.
Also, there's too much blue in the background. Look at the other icons in WC3, there's another one that looks similar to this (I think it's crown of kings +5) that's a helmet with a blue glow. The glow in those is just around the edge of the helmet, and it fades out; yours just looks like a cloud.
If I had to rate it now, I'd give it a 3. It could definitely be much better with some work, though. I like the shape of the helmet itself.