Mojang changed how they store Minecraft skins, and, it is actually surprisingly efficient.
Instead of storing each player's skin, they store the skin files in a way in which if two players share a skin, then they use the same png image for it, reducing the amount of HTTP requests Minecraft needs to make per user.
This system is cool, but, it also means that we will probably need to change how we load skins for playerheads, which, isn't a huge issue, primarily as I already wrote or found every line of code we need to account for this switch.
For those with access to MineCore files (only myself and the Admin team IIRC), I have put a few new scripts in the /home/minecore/scripts directory, primarily get_skin_url.py (accepts a UUID) and get_skin_url_user.py (accepts a playername) for a possible implementation
Another thing which comes of this is the idea of caching the heads based on their internal texture ID (which is what the URL contains), but, that could come later