MOTIVE
Your photo(s) showed a motive that is not accepted by Airliners.net. This problem may be due to a very wide range of reasons.

Some of the most common examples are:

Photos showing just a part of an aircraft (with no motivation for doing so, like a special sticker, damage etc.). Additionally, cutting off the nose or a part of the tail can also result in a motive rejection.
Photos with distracting or obstructing objects in the foreground (this is especially true for gate shots which are very difficult to get accepted due to their common nature and the large amount of equipment which usually surrounds the aircraft). Any equipment or objects blocking parts of the aircraft will result in a motive rejection.
Photos that do not show an aircraft or anything sufficiently related to aviation at all. Common examples are photos of ramp equipment, like stairs, or cars. Or airport structures like radar towers, jet bridges, office buildings.
Photos showing the date in the lower left or right corner of the image. If your photos show the date on them please disable this feature on your camera.
Close up cockpit shots with the only reason for the shot being showing pilots waving.
Cockpit photos in which the pilots block out most of the panel
Photos taken through aircraft windows that show little wing/engine and have no airport visible on the ground.
Photos that include window reflections. These can result from taking photos through terminal windows or observations decks that are enclosed by glass. Shots taken through aircraft windows can also result in reflections, or can show scratches or dirt from those windows. This will also result in a motive rejection.
Photos taken inside aircraft that only show tables, dinner trays, or personal tv's. Cabin overviews that are taken from a very low standpoint and have seatbacks block out most of the image.
Please note that motive rejections can also result from other, more subjective reasons. These are usually of an aesthetical nature.

A few examples of unaccepted motives:

Planes cut in half - Photo copyright © Javier Guerrero	Cut off stabilizer - Photo copyright © Thierry Deutsch
Grass covering the wheels - Photo copyright © Thierry Deutsch	Detailed rejection reason from a screener: "The foreground has absolutely no interest, the middle ground is cluttered and distracting, a band of interest and a lot of sky" - Photo copyright © Thierry Deutsch
Unjustified crop if it wasn't for the waving pilot - Photo copyright © Giovanni Tessari	Tree branches "hanging" in the sky - Photo copyright © Thierry Deutsch
Such a close-up has to be well illuminated to be accepted - Photo copyright © Thierry Deutsch	Another not well enough illuminated close-up - Photo copyright © Thierry Deutsch
Main subject not filling the frame enough - Photo copyright © Thierry Deutsch	Too much ground clutter and stairs blocking the aircraft - Photo copyright © Thierry Deutsch
Engines cut without clear motivation - Photo copyright © Henk Schmidt-Bergemann	Picture rejected due to visible window reflection - Photo copyright © Henk Schmidt-Bergemann

This is the most subjective rejection reason, sometimes simply that a photograph does not balance well, an unusual crop or similar. This rejection also occurs at times when a photographer tries something new but the screeners do not feel that the final image has been successful. Reasons (or excuses) for any such failure are not important, only the final image is considered. Images very prone to that kind of rejection are shots taken out the window of an aircraft showing landscapes with no highlighting detail like e.g. interesting cloud formations, snowy mountains, recognizable monuments.

The official rejection text states that photos may be rejected for motive if they are "Close up cockpit shots with the only reason for the shot being showing pilots waving", so if you want to upload a photo with a well seen waving pilot, ask yourself the question: "Does the shot stand by itself without the pilot?" If the answer is "Yes!" you shouldn't get a problem this regarding.

The motive rejection normally supersedes any other rejection so if you plan to re-upload a photo rejected for motive, ask yourself the question if you can change something on the motive. If you can't, chances to get it rejected for motive again are very high, no matter how subjective this reason may be.