I was thinking that Citadels should be larger, possibly taking up a whole tile like a city does. That would make it not look quite as strange when ships sail though them. (I'm not sure they need to be taller, but adding a moat and another level of walls outside the main fortress would be good. A moat and an intermediate size would be appropriate for Castles.)
I tried the Fanghornesque Ancient Forests, but there not quite as good as I'd hoped (still probably better than the default ones). The undergrowth seems a little too dense. I like Having some undergrowth, but I think the giant ancient trees would block so much light that that as much could grow below (then again, it has been said that in Erebus there is no Photosynthesis anyway...). I think that the ower portions of the trees should be a less dense, and that trees roads and maybe resources should pass under the canopy (you should be able to see the trees arching over them from a side view, but most of the roads would be covered by the foliage.
Edit: I just checked back in the game, and I don't think there is such a problem with the undergrowth as I thought. I think I was zoomed out to far to see it properly (when you zoom out to an angle that hides all the tree trunks then it doesn't look too good). Its growing on me now, but I still think that the bases of the trees be a little further from the road but that they should arch over it to cover it.
I think the one thing I don't like about it is the tree at the back right corner of the tile. It shape seems a little odd, at least for the corner of a tile (and it looks worse when you zoom out more). It might be fine if it were moved a little closer to the center and/ or if were a couple of smaller trees of a more normal shape nearby.
Oh yeah, I also still think that the New Forests should be a lighter, brighter color (possibly the old ancient forest color).