This is refreshingly thorough, although of course on many shots there is still room for detail especially in the first 3 teasers.
The blacksmith in the first teaser is looking nice and original.
WARNING -SPAM EXPOSURE- WARNING
In the second, (this is where my opinions most likely part from the many) I would suggest experimenting with overlapping rock formations/rubble pieces especially up on the tops of mountains where you wouldn't be able to walk anyway as it, in my opinion, lightens the restrictive grid feel on game-play. I would also suggest trying to apply more ground types on levels where there is just one grass type for nature and one dirt type for path to, for example, two or three for each. The dead tree/root extensions and ground type mixtures in the last shot are great.
This is getting into nitpicking but in the third teaser the bridges look nice but I would refrain from using too many vertical stone wall pieces(1st and last shots of 3rd teaser) for the same grid reason explained earlier. The heavy looking stone structure looks strange being supported by planks of wood in the second shot, and I would also try to refrain from using too many of the same hangable vegetation pieces consecutively (1st and 4th shots of 3rd teaser).
The 4th and 5th teasers are for me untouchable...
Great work.
[These claims may cross into the realm of 'spam inducing' and have therefore been properly labeled]