Often I think it depends on the number of people applying. It could just be as simple as someone with a little more experience or background or enthusiasm, etc. It's not like a paper and pencil test where there are "right" and "wrong" answers. I decided once when I was only doing par-time/temp jobs to send a resume out that was "me" so I put my bird in the top left corner?
It was smaller, of course, and just the all black, but I love him and think he is funny. My thinking was that I did not want to work for people who did not enjoy him (and by default, "Me") and were too stuck up or whatever to call me in for an interview. The job I got was one of the best/most useful to me I ever had. It goes two ways, getting hired. It is not just them accepting/rejecting you but you should be doing the same for them and the job. I was always surprised when I went on a lot of interviews and was disappointed I did not get a job -- the job I did end up getting was always a much better fit for me than the previous interviews would have been.