If there’s a shadow under objects as a part of the image, it should usually be soft and smooth, not too big, no hard edges.
A shadow should not be sticking out of the image borders, as it will look weird on the website.
A shadow is something dropped by an object, not parts of the background around the object.
Shadows should be neutral in color and bear no significant color casts.
High boots should not be falling backward.
There should be no fingerprints, scratches or dust on shiny surfaces.
The photographer and camera should be removed if reflected in shiny surfaces. Same with the studio equipment.
No props or pins should be visible anywhere.
Suede should not be spotted.
Smaller items like jewelry should be shot close enough (macro lens is a must), otherwise, it would be stretched upon resizing and lose sharpness