Amongst a whole bunch of rejections (which have been genuinely educational for this newbie), I've just had this one knocked back for that old chestnut of not being level.
As reference, I took both the verticals and horizontals of the building and rotated the photograph to them. After receiving the rejection, I rotated it so that the plane was level but (you guessed it) the building looks like it's built at the craziest of angles. The ground at the airfield does indeed slope like that.
I know the quality of this picture isn't cutting edge; should I just forget about this one?