NamCam is the Namco camera system that takes a player’s face photo in Mario Kart Arcade GP.
The arcade cabinet uses NamCam to photograph the player after they sit down. The game then modifies the image according to the selected racer—for example, a player choosing Mario can appear with Mario’s hat layered onto the photo. The altered face image is displayed above the character during races, helping distinguish human players from computer-controlled opponents.
This feature reflects the arcade setting of Mario Kart Arcade GP. Unlike a home-console game, the cabinet can include dedicated hardware such as a camera, steering wheel, pedals, and a screen positioned for the player. The result is a personalised visual effect that is part identification, part novelty.
Nintendo Network and Miiverse are online Nintendo services, not the camera feature used by this arcade title. Triforce refers to an arcade hardware platform associated with some Nintendo, Sega, and Namco systems; it is not the name of the face-photo system. NamCam is therefore the specific and canonical answer.