I'm not sure the crop, or the angle works for me here. I think the subject is fascinating but i can't help feeling that it could be presented in a more fascinating manner, too.
Wonderful subject, but really needs a better backdrop instead of white - something textured would have been neat. Try moving it further away from the table so the shadow doesn't show up. I like the off-center composition.
Oops, another horseshoe. I thought there was only one. The subject itself is very interesting, but the background is too flat and uninteresting. Maybe a gradient lighting.
The rust gives a very interesting texture to this shot.
Focus could be a little better and the overall it's slightly flat but a great idea that meets the challenge well done.