I love that you went with a custom design and it looks fantastic! I have no idea how you plan on making the marbling on the crest or the horse decal on the back but if you pull it off it would be very unique!
A word of warning though: making custom helmets can be very tricky.
1) approval. If you have ANY doubts on if it follows the CRLs make sure to bring it to the Q&A section or, better yet, your Ruus'alor, in our case Darnai. it would be an absolute shame to work on such a beautiful design and then have to scrap it. I'll be doing the same today regarding an asymmetrical visor I want.
2)construction. If you are making it from scratch, depending on the material, design problems will probably become a challenge. Make sure you have the technical aspects of building the helmet written down so you can refer to it, whether it's notes on measurements or a blueprint. There will also probably be some problems you didn't foresee that will pop up while building. Don't be discouraged. Try tweaking your design slightly and see what happens.
The other route is to buy a Boba helmet and modify it. Since your design is similar in some respects it shouldn't be too difficult. It might even be your best bet.
I hope this helps!