Since these pictures are out of date, I'll just review two screenshots that look the most 'complete' to me, assuming you didn't change them much.
I will say this though, overall, your trees roots are too big. Its a small detail that I wouldn't care to change probably but if you want to make it perfect, that's something that I would change. Like in the first screenshot, the tree near the waterfall--it's roots are huge but the top part (not sure what the official name for that would be...) is skinny. Same with screenshot 4, the tree in the middle of the image has a big trunk and good sized roots that fit it, but the limbs are all stubby and yet the leaves are huge. I would just widen the tree at the top some and it should look good. This problem also occurs in some other screenshots, like #6, #10, #18, Maybe even have a modeler combine the world tree with the tree model you're using for the top? Might make your job easier and getting the scale perfect easier as well.
Now for the actual review
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Screenshot #16
Overall, nice looking village area. If you were going for a more industrialist, and very populated city I would suggest switching tiles and using a cleaner looking brick for the roads with less grass patches, but if your intentions was to create a
village I think it looks perfect.
Screenshot #20
I assume you've done some changes to this area, but I thought I would still comment on it because I think it's one of the worst areas, only because it's pretty boring. I like the rest of the pictures a lot, like most everyone has said the rock statues and especially that rock dragon thing are really cool and look fantastic for some old Ogre areas. Due to using those mossy rock models and a few other things the statues all look old and dilapidating, and it's perfect if that's what you were going for. OK sorry I got off-topic, back to the screenshot at hand.
For one, and I'm not sure if this is because of the screenshot or what but the tower looks kind of lame. It's just a cylindor tower with nothing special to it. If it's old and dilapidating, maybe add some moss or vines to it, try to make it appear a bit more broke down.
If it's newer and well-used make it look like it is. Add some torches to it going around the top or at the bottom. Not sure what you're doing with this though, but like lexalex said I assume it's for a quest or boss?
Also, it has no door! At least none that I can see. Could also add some stairs going up the door if it's added

.
Last but not least it looks small! That's ok if the tower isn't a big deal, but it seems be the center piece of this little area, so it could be a little more impressive. The massive tree next to it doesn't help either, try scaling it down and maybe scaling the tower up? You might also put it nearer to the cliff or make the surrounding area smaller or raise the ground its on up a bit higher, like add a third level of elevation that the tower sits on alone as the area currently has two levels of elevation, if you see what I'm saying. It might make the tower appear bigger and more looming.
Other then that, looks great. Maybe just add some more vegetation like everyone said and if you added some nasty jaded rocks to the bottom of that cliff it might give the area a more 'doomy' feeling

which, with the fog and all, it already kind of gives me that feeling.
I hope my review was constructive! Keep up the good work, it's a really excellent looking Old Forest at the moment, something I'd expect to see in like Mirkwood or something.