Exactly as I type this on the top 5 views shots on the home page there is one CLEARLY off center (29000) to capture the other aircraft entirely, 82002:
Photo © Bruno Bevivino - Roma Spotters Club
And another that is CLEARLY low in frame to once again, capture the other aircraft.
Photo © Mark H
If I can get a screener to comment on why some off center and low (and high I'm sure) pass the test but others don't. I have a few others intentionally low as to not cut the tower. To properly center the aircraft the tower would need to be cut off at the windows and I personally think that just looks odd compared to a bigger overview of the entire shot. Also, in the following picture, "Arizona" can be found all over the place, being shot in front of the tower makes it a little different than all the rest.
[Edited 2014-07-27 10:25:39]
[Edited 2014-07-27 10:27:09]