Thanks! There will be some changes before it is finished, including a few more people on the roof. These boats could carry up to 50-60 or more passengers. No way I'm putting that many on board, but I will probably add another small group near the bow. Also need to add luggage. Hopefully there's a way to maintain clarity and composition while conveying a sense of what traveling on these boats was really like. (Every contemporary account I've read mentions how crowded they were.)
I appreciate the comments about the foliage. There are five or six species on the ground now next to the towpath, so maybe it's just a matter of making a few more variations. Leaning some of them is a good idea. And those branches in the upper right have been bothering me, too. I worked so hard on that fallen tree trunk!

But I'll have a look at that awkward branch too.
And Ulco is correct – this is path traced. I've been experimenting with ways to improve the shadow detail – increasing GI prepass padding (at 0.5 now) and max paths (now at 36). I don't think I need to add a fill light (like a plane to reflect light back into the shadows). Overall I think the natural contrast looks pretty good.