Your “beast” image embodies many of the pitfalls of a poorly composed photograph. The image lacks a central area of interest, the 4 walls of the photograph aren’t thought out and the lighting isn’t optimal to name only a few issues.
Your “beauty” image however, fixes many of these problems. With this image, you’ve implemented the boy’s arm as your main area of interest with helps give the photograph a sense of story and direction. Your beast image lacked this element of visual story telling and therefore was easy to pass over. The image with the child’s arm however, has a story in it. It’s subtle and abstract but you have the beginning of a story.
You’ve also managed to limit your color palette to a reasonable array of colors. A strong influence of purple with a red highlight help provide a nice, simple background that helps isolate your main interest within the shot and draw out attention towards the boy’s arm.
You’ve also set up your photograph to take advantage of the benefits of informal balance. Your photograph abides perfectly to the rule of thirds. The boy’s arm acts as a sort of “horizon line” which is located 2/3rds of the way down the photograph and the doorknob is located in the bottom left corner also helping ensuring your image abides by the golden mean.
Great first assignment. I’m looking forward to seeing what you create next!