I like using members' birds actually, it personalizes the banner in a way that stock photos can't, no matter how gorgeous. See the blue budgie in the middle of the current version of the banner?
That's Blinkie, probably the most iconic bird this forum has ever seen. He belongs to Bea, who later went on to become one of the founders of TC. During her time here (mostly on previous incarnations of the board which are lost forever now) she posted a ton of pictures and stories about Blinkie. There are still some pictures of him in the
photo contest section of the main website, and I couldn't NOT put him in the banner. He's part of the history of this board and he totally belongs there.