How do I get minecraft heads from a specific player skin?

Solution 1:

With the 1.8 update, how player head items store the skin has changed so that it remembers the skin when the head was created instead of updating anytime the player updates their skin.

This means that you can pick a skin from anywhere, wear it temporarily, give yourself your own head with the command /give @p skull <amount> 3 {SkullOwner:"<yourUserName>"} (replace <amount> and <yourUserName> as appropriate), and then change your skin back to your normal skin. The head in your inventory will always have the skin you were wearing when you created it.

Dinnerbone explained this new feature:

When you place a skull with a players name in vanilla, it looks up their skin as it at that moment and saves that information in the NBT. If that player then changes their name... nothing happens to the skull, it already knows which skin it wants to show and it's going to stay on that skin for all of time.

You can just change your players skin to a silly clown, generate that skull and change your skin back to normal. That skull will always look the way you just made it look, the worlds silliest clown. Go copy that nbt tag and share it on reddit or with friends or print it out and slap it on the walls of streets, anyone who makes the same skull/item with the same nbt tag will have a skull with that silly clown head