Update:

Armor and helmet has now been converted into standalone items: https://www.nexusmods.com/valheim/mods/1215

Credit:

Uses aedenthorn's Custom Meshes and Custom Textures plugins for BepInEx to replace the Drake Helm's model with a new model ported over from two (one mostly dead and one still being developed) Warhammer Fantasy mods for Mount & Blade Warband.

Model and textures originally created by Furok for the Grim Age mod for Mount & Blade Warband. Development on the mod ceased and the assets are now open-source. I extracted the particular files for this from Warsword Conquest, another Warband mod using some of those Grim Age assets. Grim Age and Warsword Conquest are both mods based on Warhammer Fantasy, and as such should be considered Derivative Works to which Games Workshop holds copyright to. Games Workshop's copyright thus extends to the models and textures used in this mod.

I didn't do anything except pop the model into Blender and re-scale/reorient it for use in Valheim, and claim no ownership of either the model itself or the framework/tools for having it be useable in Valheim.

Installation:

Install all mod requirements first: aedenthorn's Custom Meshes and Custom Textures, and BepInEx Pack for Valheim. 

Make sure that for Custom Meshes you download the optional files and follow the instructions in the optional file description. Do it manually, since apparently Vortex isn't installing those properly at the moment.

Then, just unzip the main file contents into your Valheim install directory.

Once in-game, you can use the console to spawn a Drake Helmet for quick access if you want.

(f5 => imacheater => spawn HelmetDrake 1)

Bugs/Issues:

Beards will probably clip through the front of the helmet. I'm not sure if this is something I can fix at the moment, since it seems like the vanilla Padded Helmet has the same issue.

=======Body Replacer Update======

Body replacer credit:

All credit above applies to the optional body mesh replacer too.

Additional credit to Discord users on aedenthorn's modding discord for in-depth public discussions over how to import a player mesh to Valheim, which I referenced heavily while doing this.

Battleaxe shown in the new body replacer screenshots is from armycak108's Battleaxe replacer mod.

Credit to armycak108 for moral support and keeping me going through this nightmare XD

Rigging has been adjusted a little in v0.1.1, pauldrons and arm plates look better now and the gorget was expanded a little to allow for more head movement without clipping out of the breastplate. 

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There's hefty limitations on the body replacer, hence why it's under Optional Files. Was originally just going to keep it for personal use, but I figured there's prolly some other Warhammer superfans out there willing to take a few hits to play as a Chaos Warrior now rather than later.

Still: install at your own risk. I highly recommend manual installation and management in this case to ensure all files are installed and subsequently removed properly. All paths mentioned are relative to your Valheim install directory.

To install, unzip the optional file into your Valheim install directory.

To uninstall this body replacer (you definitely will need to at some point):

delete the '0' assetbundle from BepInEx/plugins/CustomMeshes/player/model
delete the '1' assetbundle from BepInEx/plugins/CustomMeshes/player/model
delete the textures in BepInEx/plugins/CustomMeshes prefixed by 'player_0'
delete the textures in BepInEx/plugins/CustomMeshes prefixed by 'player_1'

1. Female body meshes are completely borked with the male body replacer active; I've heard this might have something to do with the fact that my mesh is importing with a different bone order than the vanilla skeleton. Female body meshes just get stretched into something unrecognizable and you may not be able to control them properly anymore either. If you're hopping over to a female character or into multiplayer, make absolutely certain that this body replacer is removed first.
EDIT: Custom Meshes was updated to 0.2.0, and this resolved an earlier issue where replacing the female mesh with the Chaos Warrior mesh would break control inputs. Female Chaos Warrior replacer mesh is now included with the male mesh in the optional file.

2. There's no head on the mesh, so you have to wear one of the Grim Age helmet replacers. Unless you like the idea of being headless. 

3. You may have to reload textures sometimes to get them to apply properly, I usually have to log out and log back in to the same server with whatever character I'm using. Will try to look into why this is happening, but it's of a lower priority to me at the moment.

4. For the smoothest experience, you'll want to equip only a helmet and your weapons/shield, and have no hair or beards. This has to do with the attach points being borked right now, which I believe is a current limitation of Custom Meshes. EDIT: You can use https://www.nexusmods.com/valheim/mods/410?tab=files&file_id=1586 to mitigate the effect a little, that mod disables chest piece and cape visuals. After some further personal use I also found out that both Leather Pants and Troll Leather Pants interfere very little with the player mesh (they just recolor some of the sharp planes sticking out of the back fur); so you can actually keep a halfway-playable set together.

5. I rigged this up super haphazardly, so there's some noticeable jank in the mesh even when it is working to its fullest potential. There's some stray sharp planes hanging around the back of the fur, and the textures don't apply to the gloves and boots properly right now. The fingers aren't actually rigged onto finger bones.


6. There's no telling how much will break when Valheim or Custom Meshes update, and I'm not entirely confident in my own ability to fix bugs with this player mesh when they come up. 

I'll see if I can draft up a similar process document to my helmet replacer one, but I need some distance from this for a few days XD