To get custom player heads, all you have to do is type a command. No mods, plug-ins, or downloads required.
The command is: /give @p 397 1 3 {SkullOwner:"larryboy592"} That is the command for MY head. To get your head, or the head of any PC edition player, do the same command, but where it says larryboy592, insert whatever username you want. WARNING: This command is caps sensitive and won't work if there are any caps where there aren't supposed to be, or if there aren't caps where they are supposed to be. You have to have the quotation marks where they are supposed to be, along with the curly brackets.