What is the highest number of airliners shown flying together in a single photo?
The image found here shows 13 DC-3's in formation which were used as airliners at one point but these are in military livery in the photo.
Here is the kind of photo you describe but only 3 aircraft are in view. Keep in mind aircraft are generally turned onto the final approach path and only a few may be lined up straight off the runway at any given time.
The airbus operation you link, may be the biggest instance of passenger jets flying in tight formation.