FOSS gamedev and creative worlds

In our mod nssm we have really a lot of textures for the different mobs and tools. So we were trying to sort all of these textures pngs in the texture folder creating some subfolders.
The problem is minetest can't find them and creates dummy image for them even if the path specified is correct (I checked this, when minetest creates a dummy image it tells you where it was looking for the image and the path it gives to me is the good one).
So I would like to know from someone who knows the core of minetest if for some reason one cannot place textures in subfolders.
Thank You

It simply hasn't been added yet.
You could split the mod into serveral different ones with a main one to provide the API functions and combine the whole thing to a modpack.

Thank You