PaparazziGnome automagically takes a screenshot (including your user interface) whenever you level up, gain an achievement, or kill a boss.
It has no configuration options or ingame slash command.
Screenshots will be take after a small delay of 1.25 seconds, and after taking one screenshot it will wait 120 seconds (2 minutes) before it takes another one, no matter what happens. While you are in combat it will never take a screenshot as triggered by a boss kill, so it won't take multiple screenshots when killing the Four Horsemen in Naxxramas, for example.
If you want to request a feature or report a bug, please visit the ticket tracker for PaparazziGnome on wowace.com.