As I am looking at this there is one thing that stands out to me the placement. You are cropped so tight on the right side that you should have balanced it out by cropping tighter on the bottom.
Your lighting seemed to be fairly good here you only have a small amount of glare going on. You also have good detail.
I don't see a true white background though I see a bit of a pink hue, probably from working in sepia mode.
If I had to pick one thing here though that hurt you in this challenge it would be the subject...the unicorn just does nothing for me here, I'd rather be looking at more detail to the cuts than the pewter figure.
I like the idea. The unicorn and cystals brings out enchanted and mystical thoughts. I might have used this shot for a different challenge such as fantasy for example.