How to get a character's head picture?

Bit of a goofy question I suppose, but I can't seem to find the answer.

Now I know that you can get a player's avatar picture by using http://www.roblox.com/Thumbs/Avatar.ashx?x=150&y=150&Format=Png&username=, but I don't want the player's avatar. I want the picture of their head that you see when you visit a profile.

An interesting thing I've noticed (not sure if it's relevant), when using the link http://www.roblox.com/Thumbs/Avatar.ashx?x=150&y=150&Format=Png&username=NathanTheDeveloper it shows the avatars picture and sends you to the link http://t7.rbxcdn.com/4cd0cbcc17be8f32bc10eddaab508e30; however, when going to a person's profile, right-clicking their head, and then clicking copy image address, it gives you this link https://t0.rbxcdn.com/fefb4208a69e2466320b8ea2c7de99b1 which has a few differences.

First, you'll notice that at the beginning of each one, there's a t followed by a number. Perhaps this signifies what you're looking at? 7 being the full-body picture and 0 being the head picture? They are also followed by a bunch of numbers and letter than have little, if any at all, similarities.

I tried using this information to find the solution, but I'm still having issues.

Does anybody have any solutions?