A "mugshot look" typically refers to the style of photos taken by law enforcement when booking suspects. These photos are characterized by:
A front-facing, emotionless expression
Harsh, unflattering lighting
A plain background (often with height markings)
The subject holding a placard with their details
Or, you can simply think "celebrity after a 3-day bender" meets "just rolled out of bed and into a police station." It's an art form, really (smile).