Thank you, mttriglav, for all your work on this and sharing it with the community. It's fantastic and I love it.
Notes for users new to using mods for FE (like me) or just a little dense in general (like me).
If you have a normal, default Steam installation, the unzipped file named "TNP" goes in "...\Documents\My Games\LegendaryHeroes\Mods\Gfx" (I put it in "Fallen Enchantress" directory at first by mistake and was surprised at how "subtle" the mod was, haha. So subtle it was like it wasn't even there, more like.)
If using the tree mod as well copy the unzipped .dds files into the "Trees" folder in "...\Documents\My Games\LegendaryHeroes\Mods\Gfx\TNP\Gfx\HKB\Trees" and overwrite the existing files that were there.
Start Legendary Heroes and select "Use Mods" in the Options. It will require the game to be restarted. You will notice the improved terrain immediately. Grassland, dessert and mountains are all clearly improved.
Play around with the games brightness and contrast setting in the advanced options. They make a big difference in how much the new tiles pop out.