Sweet. Yeah, on the pauldron, make the eye sockets less round and the brow bones sloping a little bit more. Horror prop skulls tend to have more pronounced brow ridges, different shaped mouths and eyes, etc. than actual human skulls, for exactly that reason -- to make them look more sinister, because a human skull sort of... doesn't, in a weird way.
The helm plate doesn't look like a cow skull to me, it looks like a flat face plate rather than an actual part of a skull (even a made-up demon skull). It's flat and doesn't have any sort of projecting face, and doesn't look like it came off the front of a three-dimensional skull either. I would say just make it that way, like a plate that goes over the front of your head, and make the horns separately just to get them all in the right places.
Ori the Dwarf
Urania, Muse of Astronomy
Random steampunk wardrobe items