I really think you hit a home run with the trees, but they almost are your undoing in this scene, because my eye goes to them and not to the action around the caravan. I think a really bright and varied environment would work better with a simple setting like a solitary figure walking through the forest. That way, the trees can be the main attraction without distracting from the focal point.
That said, I think you have a great concept here, and I really like the wagon design and the varied figs, particularly the captives. The horse hitching is a really nice technique as well. It looks like there are a lot of articulation possibilities with it.
A last item would be that I'd like to see the bad guys either carrying or dropping weapons as they run away. You'd think they would be armed with such a valuable cargo. EDIT: after looking at the full gallery, I see some of them with weapons. I guess they just weren't visible in the shots you show here
Keep up the good work!