Recently a few screenshots of Avatars in the Player ID of Halo: The Master Chief Collection were revealed on Halo4Nation (which I'm thinking they got the images from PAX). 
  
  
 
  
  
The above image shows Avatars: Halo 2 & Halo 3 Arbiter (I'm assuming), Jul Mdama, and SGT Johnson. The Player Emblem seems to be on the right of the images 
  
From what we can see the Player ID consists of:  
  
- Emblem & Color Customization 
- Avatar 
- Service ID (I think like B312, N00B, or B00) 
- Clan Tag 
- Roster Nameplate. 
  
UPDATE: Another screenshot of Master Chief Avatars from Halo4Nation, and updated Cortana/Palmer screenshot. In the spoiler below. 
  
Player ID screenshots: 
  
 
  
  
  
Then we have Spartan Armor customization revealed by Blake BellaMoMa, and Elite Armor customization (revealed by muah). 
  
Spartans: 
http://www.343industries.org/forum/topic/37554-spartan-armour-revealed/?do=findComment&comment=335598 
Elites: 
http://www.343industries.org/forum/topic/37531-some-h2a-elite-armor-revealed/?do=findComment&comment=335250 
  
  
That's it. Thanks for reading!  
- - - - - 
Thoughts? 
SOURCE: Halo4Nation 
http://halo4nation.com/master-chief-collection/halo-2-anniversary-elite-armor-screenshot/