I had a third image "selected" for the Nikon Stunning Gallery. I use quotes because I’m not sure what kind of selection process is going on. In order to place a photo in contention, you add the tag nikonstunninggallery to any of your Flickr photos. I’m guessing some ‘bot does the processing, because I’ve seen the same image pop up in the gallery a couple of times. There have also been rumors of shots taken with Canon cameras appearing in the gallery. I guess as long as they have the tag, it’s OK.
Even with ‘bots sorting through the tons of photos that must be submitted, the quality of the images is quite good. Either Flickr users are being very selective about what they tag, or there is some human review taking place. More likely, it’s the former.