Now all of you have probably wondered, how do I get a custom player head in vanilla minecraft without programs?
Now your answer has been answered with the 1.7.2 update and above!

Now your asking, but how?

Here's how:
First your going to need a command block.
You don't actually need this you can just use the chatbox.

Next:Get a power source(duuuuuuuuuuuuh...).

Then place the command block and type in the command:
/give @p 397 1 3

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Note:It is very important that you have the damage value of 3 or else you'll just get a Skeleton Skull.

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Then insert the data tag:
{SkullOwner:#}
Inside the # place the name of the player you want.

Then there you have it you now have a custom player head of your choice!