Thank you Eishiya for the remarks. It's edited :)

The metal bars on the door and barrel appear to create indents, rather than being attached to the surface, because both cast very soft shadows, both above and below. On the barrel in particular, there should not be extra shading above the bars, and it should be smaller below, because the hoops are very flat (both in reality, and in how you've drawn them). A sharp, one-pixel shadow would probably look more natural, and wouldn't distort the form of the barrel so much. On the door, some shading above might be "excusable" as ambient occlusion, but not as much as you've added.