Currently there is a project with a high resolution for a 512x Levathian Axe texture for a trident:
https://www.curseforge.com/minecraft/texture-packs/leviathan-axe-trident

I was wondering if it would be possible to collaborate with the author for an enhanced alternate appearance.

If that is not in the cards, I'd gladly settle for an explanation how one could change the texture of the weapons or at least the Levathian axe. I've personally gotten rather stuck on how the .geo.json files work.

Sure, I'll send a message to maybe add a builtin resourcepack of that one for the axe or something like that.

As for the .geo.json files, those are geckolib files. If you are familiar with blockbench, then you can install the geckolib plugin, this makes you able to export .geo.json models of the item or entity you've made. All in all, it is still the models/item/leviathan_axe.json item model that determines what it should look like, so you can still override that file to anything you want. The leviathan_axe_charging.json file is the model for how it looks when using it to throw it.

Thank you for the advice, I was able to get it going with that addon (had no clue you could even do that in blockbench). Unfortunetely the animated textures are beyond me, so I'm holding my fingers crossed for that resource pack.
Loving your mod, amazing work :)

Animated textures are quite simply actually! As long as you aren't using geckolib models that is, I've never tried to see if it works with them. With normal item json models at least (which you can overwrite the leviathan axe one to not use the geckolib model by getting rid of the builtin entity line at the top), you simply add a texture containing each frame of the animation, for example if you want to animate a diamond with 4 frames, then you need to add a texture file with the height being original size * number of frames, so if the texture is 16 px then the height will be 16*4=64 pxs. Each 16th row is one frame, so just make your texture changes for each frame. Once that is done, you need to make a .png.mcmeta file containing details on how the animation should play out. I suggest looking at the lost_soul.png.mcmeta or moonstone.png.mcmeta and their respective images for more info!

Hate to break it to you, but it doesn't seem like I'm getting a response from the creator. You can still attempt to do the translation of the model yourself, but I don't want to do anything/add the changes unless I get a confirmation from the creator naturally. Gonna leave this issue open out this weak then close it.

Oh that is very disappointing, I’m still holding out the other author responds.