I agree with the previous comment. The scene feels a bit plain as there is not a lot going on, maybe a few plants on the ground, perhaps some ivy and dirt on the coffin to show that time progressed, also working a little on texture of the coffin, because like warkama mentioned, it’s just way to clean for your scenario.
Another thing is the lighting.While Darkness works in this scene, it shouldn’t be too dark, as it’s easy to miss out details that could help telling your story.Lighting will also help emphasizing your focus, but i will talk about that a little later. I see that you already choose a blueish tone, which works perfectly fine in your case, but it needs just small percentage of a warm tone, which could come from e.g. small fireflies, or some lighting orb between the models that shows they are about to merge idk.
about the focus and composition, it is , again, important to keep in mind what you’re trying to tell. On sketchfab, its possible to turn your artwork around, but wether its a rendered image or not the viewer should get a clear first impression, at least im my opinion. In your case, the soul already drags a lot of our focus because it is the brightest element, but bcause of your camera offset, this effect is weakened, so you could put the models more in the center. TIP: Rewatch your artwork after a few days and try notice where your eyes are wandering of, you will see what i mean. here are some links that could help your story telling:
Blenderguru Artcritique series:
CGBoost has also a few artcritiques worthwhile watching, you can give it a try
bguru has also videos about the understanding of color etc. Even today i keep rewatching those artcritiques for tips for my work.
At last, sketchfab has a handful but powerful filters that can boost the impact.You can play with these.
But this is an interesting concept for an artwork