There are some very good looking forest reskins, like TO’s one, but it’s missing falling leaves in the area. Standart and Q forest have it. What it depends on?
Falling leaves (just like smoking chimneys or cave waterfalls) are animated loops that are part of the tile model. Right-click a tile to open the tile properties. If the animation loop 1-3 boxes are greyed out, the tile has no animations, otherwise you might check the boxes to activate them.
I thought about that, but of all that I’ve seen only Wild Woods trees with luminous bushes have active animation loop boxes, other trees do not have. Yet, even WW trees’ animation doesn’t work in that particular reskin hak (mark or unmark - it changes nothing).
In that case I am 99% sure, that the reskin is the problem.
If the animation loops are still in the tile but nothing shows up, the reskin probably doesn’t have any texture for the animation parts of the model.
Shouldn’t it then use a texture from standard forest tileset?
Anyway, I checked all the DDS and TGA textures for ttf01 and didn’t find those orange leaf and little light which fall down from the trees in forest areas 
Afair tiles usually have only a single texture so if a reskin replaces that texture and has nothing where the animation texture is supposed to be (a black area) then the animation is running “invisible”.
I haven’t checked it out myself for NWN but that is how textures work in those engines where I did some myself.
Well, I’m now checking SET file and standard models with working animation, but can’t find any clues inside so far. AnimationLoop strings are the same for every tile and models have bitmaps for tree crown. That’s all, nothing else related to leaves or animation (at least I don’t see it).