Slightly off center works well here; I like how it suggests here that the shoes go onward and are part of an environment that we can't see. Here's a dumb comment, but I wish the shoes were older or had more character to make them more intresting. Nice work anyway.
i don't like the framing of this shot much at all. you've cropped off a lot of the subjects and it kind of looks awkward. lighting is decent, but i would try to boost the contrast a bit with some more directed, brighter light. 4.
There is another shot of boots, or rather, A boot, and I commented to them that I wish both boots had been in the shot! I like this shot, your focus is wonderful, but the composition is lacking something for me. I would have liked to have seen something a little more dynamic. I think the shot works very well for the challenge.