How do I do that for the Flappy Bird one? I can get a screenshot of my high score - 44 or so - but how do I show a username...put it on paper, then get a picture of the high score and the phone?
For mobile games we tend to just allow direct screencaps to be submitted. If the game supports Google Play / Game Center leaderboards like this one, then screenshot the logged in leaderboards view.
edit: http://arcademy.net/forum/index.php/topic,157.msg1398.html#msg1398