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.