You are right that the monochromatic elements of this photograph worked out very well. The two predominant colors in both your background and main object are varying shades of green and brown.
The composition and simplicity of this image is great. It is what we asked for, but what I would like to see you try and accomplish in future assignments is to focus on larger areas. The idea is to try and break away from the safety of close up images. It’s much more complicated to organize chaos on a larger scale. You’ll need to consider things like shapes, lines, areas of focus, the way an assortment of colors communicate with each other and so on.
Most importantly it gets you thinking about your positioning. When you are not focused in on something close then you need to put considerable thought on your placement as a photographer. Just finding the right place to take the picture from can take 30 minutes or so.
That all being said, the image you’ve submitted is not wrong. However, for future assignments, try pulling your camera back a little further and incorporating large scenes into your shots. Use strong primary elements, depth and all of the technical organization components that you would in a more close up setting, but try to apply it to a larger scene.
You have an eye for styling a photograph. Now we just need to see you do it on a larger scale!
All the best!