You need to work on your perspective. All the thumbnails look wrong because none of them have correct perspective, In your thumbnail sketches, you need to work out the layout of your scene and the proper perspective, as well as the most effective camera angle to convey the vibe you want for the visual narrative. Your sense of composition and camera angle is too utilitarian and not creative/interesting enough. This is a very common mistake that beginners make–they are often limited to only visualizing their scenes as if depicting a theater stage, and don’t think about all the different possibilities such as interesting/dramatic camera angles and using variety of different focal lengths (such as ultra-wide angle, worm’s eye view).
Take some time and learn the basics of perspective (learn how to depict at least one, two, and three point perspective)–it is a requirement if you want to depict credible looking environments, and absolutely necessary if you want to be able to depict different camera angles.
I will look into it.