I was thinking of making an incursio myself, great reference pics by the way!
The first thing I thought of when I saw incursio's helmet was the tesla helmet from fallout 3, side by side they're not terribly similar, but to me the eyes and wing-type things off the sides of the forehead are somewhat the same. As for the horns, do you mean the little spikes on the top of the helmet? My first thought is two pieces of craft foam glued together on one edge and spread out to create a sort of backwards hood scoop on the head (it's hard to describe with just words, sorry)
Good luck!