You can now use custom player heads.
Example:
item.setSkullOwner("<playerName>"); // Item material should be 'SKULL_ITEM' for lower versions and for higher versions 'PLAYER_HEAD'
New methods:
core.playerHead(String) // Returns item with the head of the player with the name you specified.
core.playerHead(String, ItemStack) // Instead of creating new item it will change an existing item.