I like the coloring on the base, making it look like an old wood. I think however on the pads of the wheel I would have used a black for the center, only because and all metal wheel with a flat surface would have been impractical, but it is a piece to a make believe games, so practically gives way a bit. Also on the basing, toward the rear of the wheel, why not make it look like the ground had just been run over?
Over all, great job. I hope mine look as cool when I decide to paint them.