It has never been explained really but for each series a model has there are two photos that preview it. Typically the newest Preview photo is the latest series that model has available. In some situations, models haven’t been updated since the start of the website (December) and sometimes those pics will change to stay somewhat fresh. At some point we will seperate the current and updated models to those who are not. A couple of the models will be back and some won’t. Most of the new models should be with us for a good long while.
One thing we will look at in the next coming months is providing a little more model information or a page more dedicated to them where they can add some personal touches.