I really love it. Like many others here I'm not sure if it fits Rhino well even if he's the bulky one but this thread isn't about that. Just some general suggestions on the helmet on it's own.

1. The horns: I like that the horns are glowing but I think it would improve everything if you'd put a little bit more texture on them. Let them look like an old tusk of an elephant (I'm only talking about texture).

2. Tint-mask: The placements of the tints are already good. Just add a little bit of details here an there but don't let them look too random. Place them well and you'll be good.

3. A complete skin: Maybe, just maybe, consider to make an actual skin and not just a helmet. This way I'm sure your chances to get this accepted will be a hundred times more likely.

4. >>work in progress<< (I don't know any more suggestions but I believe I can find one or two more little improvements for you. But remember: those are still just suggestions and it's on you what you do with it.)