Thanks all for your responses and input.
Although I would characterize myself as a chronic letter-writer (and have gotten pretty positive results over the years from airlines, hotels, etc.) and I'm sure plenty of others here fall into that same category, I think it's fair to say that most people will not bother to send a letter, write an email, or complain by any medium. Even though complaining has become so much easier with email, twitter, facebook, etc., most people either don't know how to do it right, or will not find the time. But I believe that many of those same people who won't take the time to write/email a complaint to the airline, will still take a couple of quick photos and upload them onto a website, if the interface is simple enough. This minimal effort will provide a valuable reference for any other passenger to show the airline what good or bad kosher meals may look like, where there is room for improvement, and which airline (and caterer) has really done a great job.
There's no question that everyone (and especially those with status, and those flying business or first class) should be sending emails to the airline whenever they're served a sub-par meal. But the people at the airlines who are receiving these complaints most likely know very little about kosher meals. They don't know how bad or good your meal was, relative to what their competition is serving. They don't know that your meal in first class may have been identical to the meal served in coach. They probably don't know that the same caterer whom they sourced your meal from, is currently making a much better meal for one or more other airlines. They may not even know that it's possible for a kosher airline meal to look and taste good. They probably don't realize that they are serving far superior meals on the same exact plane when it returns from Europe, Asia, etc. They most likely don't realize that they have the option of serving a kosher passenger in first or business class on new china and with new flatware, as some airline have arranged with their kosher caterers.
So although sending emails is obviously the most effective method of effecting change, I think that an email only provides an individual's perspective, without sufficient reference points or depth of information to let an airline know what options there are in the kosher market, and how they could improve their meal offerings. The ultimate objective would be to move the under-performing kosher caterers to a higher standard, either on their own volition, or at behest of the airlines. It may be less realistic to expect any dramatic improvement in coach meals, which airlines probably budget a very small dollar amount for, but efforts like these should certainly have a positive impact for meals in business and first class, and any increased focus on quality of kosher meals should hopefully lead to overall improvements of standards across the board.
Bottom line.... The airlines don't get enough complaints about kosher meals, but also aren't aware enough about options and alternatives in the kosher meal market. I think they need pressure and education. I would encourage everyone to reach out to the airline when they have a bad meal experience. But I think the website would also be a really useful tool to collect information, help educate the airlines and push the PR pendulum.
My web design skills are pretty limited, but I'm wondering if anyone here with the requisite web design skills would take this on as a pet-project. (I'd be happy to assist in any other way.)
Please reply here if you'd volunteer for the task, or feel free to share with anyone else who you think could help with this.