How Does Wynncraft Handle Skulls And Skins?

So there are a lot of custom skulls and skins in wynncraft, and i am wondering how they make them. (And with make i mean how do they implement them. Not how do they create the textures.) I looked on google but there i can only find sites with pre-made heads like minecraft-heads#com but no one explaining how to actually make them. It's also very possible i'm just blind. I did find something about encoding json files in base64 and using the output string as a texture value but i have no clue how i would go about that. Can anyone enlighten me?

 

Update:
I've realised how they do some of the "heads". The loot boxes you get before weapons are identified are not really heads. They are a re-textured and re-modeled version of a stone shovel. You can find the textures in the resourcepack under

Code:

textures\wynn\weapons\loot

I can't seem to find other textures at this time. I could solve this by a simple F3-H on a "head"...

 

Hello, Gilles,
Kiaria from Minecraft-Heads here.
Some of the textures you see are, as you guessed, re-textured versions of MC items that show through the server's resource packs.

A lot of custom textured heads are used by Wynn as well. I'd love to meet the Wynn staff who design textured heads so we can compare notes.
The Wynn builders do wonderful tricks using invisible armor stands and custom skulls to add their detailing, which can give a different size, angle, or "look" to custom textured skulls.

If you are curious about how to generate a custom skull, you can use the generator at Minecraft-Heads after you have designed a pattern on the head portion of a MC skin. Follow the instructions listed there.