mug on the camera
“Mug” means ugly. So, there’s no other way to sum this phrase up other than “the ugly person in the group photo”.
Alicia: This hoco pic is amazing. I can’t even explain what’s going on with Jenna though.
Dominik: She’s the mug on the camera, Alicia.
Dominik: She’s the mug on the camera, Alicia.
mugging for the cameras
Making outrageous faces to grab attention while on camera.
John was totally mugging for the cameras in the background of that news story.