I didn't see any black line when playing the game.
Try to set the tiledbackground Y size in minus: e.g ( -20)
This will solve the black line problem.
Sorry, I can't understand your comment, are you saying I need invert the Y axis of the tiled background?
That is the line like I can see in a 22" android tablet:
And this is the 256x256 tiledbackground:
Can you say me what property I need to change in the panel of the tiled background?