I just want to add a few comments to how the cart was constructed. Below are screen shots showing the cart without mirror and array modifiers. I wanted the boards in the very back to be unique, so I did not mirror them.
For detailing, I looked upon the Treasure Chest project. The treasure chest was probably buried in sand, exposed to a lot of salt elements, and thrown around on a ship deck. I view that this wagon does not need to be as beat up as that. Does it have wear? Absolutely, but I tried to give it some character while hopefully not putting in too much in cracks and dings.
I also did not put in hardware, such as bolts, screws, etc. Two reasons for this: trying to keep the cart as low poly as I can and trying to stay true to the original concept art. Having said that, I did model a guide to keep the axel in place underneath the cart. No one will probably see it, but it struck me that it would be an incomplete construction without that.
For some boards, I would detail the first, copy it and rotate it on two axis and use it as another board. So, the second board would be the same but on its opposite side and upside down. Just trying to minimize my work.

