Bug #1: Skulls won't keep their item name.
Bug #2: Skulls always have the default Steve texture on mobs.

Steps for #1:
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1. Take a custom skull, for example "/give @p 397 1 3

{SkullOwner:"MHF_ArrowUp"}

". The inventory name says "MHF_ArrowUp's Skull" for now.

2. Place it on ground. The server generates the log entry: "Server thread/WARN: NBT tag SkullOwner was of wrong type; expected TAG_Compound, found TAG_String".

3. Take the placed skull back to inventory. The item name changes to "Head", though the custom skull still shows up if placed in-game again.

Steps for #2:
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1. Summon a mob with a custom skull by using a command block. For example "/summon Skeleton ~ ~1 ~ {Attributes:[

{Name:generic.movementSpeed,Base:0.001}

],Equipment:[{},{},{},{},{Damage:3,id:397,tag:{SkullOwner:MHF_ArrowRight}}]}"

2. Once again, the server responds with "Server thread/WARN: NBT tag SkullOwner was of wrong type; expected TAG_Compound, found TAG_String"

3. The mob's head has the Steve texture instead of MHF_ArrowRight's head.