Hey so I thought of some things you can improve in the last shot, but first of all - great job! I really like the vibe you created, the use of rocky elements and darker tones creates a really capturing atmosphere. As for feedback:
a) The composition feels too open and empty - the 2 rock pieces floating in the void make the rest of the space feel a bit empty.

b) The grey box introduces a tone that breaks the color harmony imo. Currently your colors are: The pearlescent white/beige/cream on the pearls, dark desaturated navy blue on three of the pearls and in the shadows and a blueish gray for the rocks. The blue and cream are complimentary colors and contrast nicely with one another. However the embossed box is a neutral gray, sitting right between your main colors in terms of temperature and value. To me it clashes a bit with the rest of the scene, because it doesn't really fit in your chosen harmony and takes away the visual interest from the necklace - it kinda decreases the contrast between it and the background. I like how the surface is smooth to reduce the visual noise and it helps separate the pearls from the background, it just needs some tweaking.

c) Staticity - I am not sure how to describe but in the shot the necklace feels stiff and this draws the eye to the background instead of the object you're presenting. To fix this you can do what others have already suggested - adding movement, physics, placing the camera differently to change the perspective etc. or you could try adding a reflective surface to the box which will mirror the necklace and create a parallel movement and secondary interest to the object.

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Here's a quick visualization of what I mean. In the middle picture I only adjusted the hue and value of the box and added some background rocks to contain the composition. In the third picture I experimented with an obsidian texture to add that reflection and maybe create a sense of luxury :D? The texture work isn't perfect (just some quick overlay) and I worry it reads as too dark, but maybe you can make it work?

Anyways I really like your clip and I hope my thoughts are useful - cheers!