The reason they look so bad is because they only have a single curve to them, unlike the horns in DoW that are more organic and wave-like: Single-curved horns tend to look damn sexy tho when they're used properly, like on the Kranon model or as Terminator Tusks: So i'd say make the horns look more organic and demonic, like @vampire_dio 's demon from Legend, because right now the horns look like they're made out of metal and that's just not the Chaos aesthetic. The helmet as a whole throws me off too. And I think it's simply because there's too much space between the mouth guard and brow ridge: As opposed to the current GW model that looks exponentially more badass (notice how the mouth guard reaches the brow ridge): Keep in mind I also realize and understand the fact that this is pre-alpha, and I don't think this iteration is final, but I do believe it can be greatly improved.
Not at all our genesires favorite son has been known to use illusions (the kind of illusions that have the same abilitys like him) before we will treat this situation as another scheme by Ahriman!