UPDATE: The redeem site for the code is now live at callofduty.com/personalizationpack.

Here’s some more info regarding the pack:
You have to have a Call of Duty profile linked with either a PSN and XBL account. The code you redeem will ONLY work for ONE console family. Meaning if you choose your Xbox account, the personalization pack will unlock on Black Ops iI and Ghosts on Xbox ONLY. The code will give you for Xbox 360 (Ghost & Black Ops II) and for Xbox One (Ghosts). Same for PSN: if you choose your PSN account, the content will only be available on PS3 and PS4. If you want one for both console families, you will have to preorder twice.

NOTE: When you redeem your code, it says that “Your personalization pack will be available in game within 24 hours” BUT, the content will only be available starting May 13th, 2014. 

Here’s an FAQ:

Where can I pre-order Call of Duty®: Advanced Warfare in order to receive the Call of Duty: Advanced Warfare Personalization Pack?

The Call of Duty: Advanced Warfare Personalization Pack is available at the following retailers when pre-ordering Call of Duty: Advanced Warfare.Please note that this list may not be complete, and is subject to change. If you are unsure about a retailer’s participation and want to receive the Call of Duty: Advanced Warfare Personalization Pack, be sure to ask before you pre-order.

3. I have a code. How do I get the Call of Duty: Advanced Warfare Personalization Pack?
You can unlock the Call of Duty: Advanced Warfare Personalization Pack by entering your code atwww.callofduty.com/personalizationpack. Before you can enter your code, please follow the steps to log into your Call of Duty® account, or create a free account.


8. On which platforms is the Call of Duty: Advanced Warfare Personalization Pack available?
The Call of Duty: Advanced Warfare Personalization Pack is available in Call of Duty: Ghosts on Xbox One, Xbox 360, PlayStation 3 and PlayStation 4, and in Call of Duty: Black Ops II on Xbox 360 and PlayStation 3.

9. I own both Call of Duty: Black Ops II & Call of Duty: Ghosts.  Will I receive the Call of Duty: Advanced Warfare Personalization Pack in both titles?
Yes.  Upon successful redemption of the code Call of Duty: Advanced Warfare Personalization Pack will be available in both titles as long as they are on the same console platform.  
 
10. I have both a PlayStation Account & an Xbox Live account linked to my Call of Duty Account.  Will I receive the Call of Duty: Advanced Warfare Personalization Pack on both?
The codes are platform specific.  The content will only be available on the platform you pre-ordered Call of Duty: Advanced Warfare for. 
 
11. After I successfully redeemed the pre-order code how do I access the Call of Duty: Advanced Warfare Personalization Pack?
If you have redeemed the code prior to May 13th 2014, the content will not be available until May 13th 2014. If you redeem the code after May 13th 2014, it may take up to 24 hours for the content to appear in game.

Get Advanced with Call of Duty: Advanced Warfare at GameStop! http://gamestop.com/callofduty

PowerUp Rewards members: Pre-order Call of Duty: Advanced Warfare to get a custom in-game Personalization Pack!