Single player problem:
When a player head is obtained using /give, player heads render as Steve in the inventory. So far the only way I have found to update this is to wear the player head, which causes it to update and render correctly. Updating it this way only works in a single player game. When I loaded up a server with Snapshot 14w30a and summoned a my player skull, it also renders as Steve.

Server only problem:
The difference with the server is that when I put the skull on my head, every item in my inventory is Appearing outside of the GUI (see screenshots bellow).
Closing and opening my inventory again does not update the graphical rendering. (Tested for both survival and creative mode, they show the same problem). Another problem I noticed when wearing player skulls is the rendering of the player model in third person mode (see screenshots bellow). Along with this player model issue, the player heads you wear do not show up. Relogging does not fix this issue, neither does restarting the server, the client or the computer. The player rendering issue only happens on servers. I will add to this bug report if I find anything else.

Edit:
The hot bar GUI renders correctly when the inventory is not open, but items in the hot bar migrate to the left of the screen when the player opens the inventory.
Player model rendering issue on servers also happens in 14w30b (I know it came out like 3 seconds after 14w30a but I'm just trying to keep this thing up to date.)