How to manipulate the camera in Fortnite Creative and Battle Lab?
I would guess the best way to take a good picture would be to use the Replay mode
So go in a game, and place yourself how you want to be seen in your photo. Then complete that game (killing yourself is fine)
Then load the game in the Replay mode, and that should give you the possibility to enter freecam mode. Where you can put the camera whereever you want.
So that should give you the possibility to take any shot you want, without having to fuss around to figure how to get the shot in the middle of a game where you get shot.