If you'd prefer to be able to adjust the head and body sizes of individual soldiers, please see my new "Enhanced Soldier Customization" mod.

This mod increases the size of your soldiers heads. Why? Because it looks hilarious. And it's FUN!
For even more fun I recommend you also install my "Maximum Carnage" mod:
http://www.nexusmods.com/xcom/mods/561/?
  
I recommend that you install this mod using Long War Mod Manager (http://www.nexusmods.com/xcom/mods/620/?). Alternatively you can use PatcherGUI 7.1 or better if you wish. It's only been tested with Long War 15f but it should work on any version, including vanilla Enemy Within.

By default the heads are scaled by a factor of 2. To change the scaling find these lines in the patch file and change the values after the "%f":

//*************************** SET SOLDIER HEAD SCALING HERE *************************
// ** DEFAULT is 2.0 - Change the 2.0 on the next line to a different value:
ALIAS=ScaleFactor:<%f 2.0>
//***********************************************************************************

There are some clipping issues with the very short hairstyles when the soldiers are in combat. To try and minimize this I've scaled the hair up by an extra 10% during the tactical game. Helmets are scaled up an extra 5%. The hair can thus look like it's floating slightly if you zoom right in.
  
There are also some issues with hairstyles that have animated pony tails - the pony tails end up slightly inside the head area.
  
For best results put helmets or caps on you soldiers and avoid using very short hair styles. 
 
1.0a - Initial release. Big helmets only for now...
1.0b - Allows soldier/MEC helmets to be scaled differently.
1.0c - I figured out a way to make BIG HEADS work properly! Not just helmets any more! YAY! MECs no longer have a separate setting.
1.0d - Tweaked to try and reduce hair clipping issues when soldiers heads are bobbing around while moving