Hi,
Those would be from Mike's memories, select the Memories tab just under quick start from the main menu - select Mike on the left then click the photos on the right to read those stories and unlock those CGs (Assuming you've unlocked them by playing the main game).
As a tip - under the Quick Start tap there's a CG Checklist with some small hints of where to get CGs. I'll also add it to the CG Gallery for the future patches.