How can I improve Happy Birthday?

I need help. On another stock photo site I was told that this image had poor lighting, that is was unusable due to composition and cropping. However, this is the EXACT image from my camera. I did not do any cropping to this photo at all. And that it is a possible copyright infringment?? Can you explain these? I am new here and to photography and I want to learn and get better. Thanks.

Thanks again Michael. Yes, the duck was the only thing I could think of that would cause a copyright infringement. I will definitely watch now what is in the shot if I want to use it later. This was taken back in June way before I ever thought about shutterpoint and other stock photo sites. I just really liked the looks of the pic and thought it would be a good one. I am really learning alot about focus and what to do and what not to do by submitting several of my photos.