The Witcher 3 HD Rework Project
While The Witcher 3 is a beautiful game, there are some textures that could be made even better. This is where the Witcher 3 HD Rework Project comes in, which you can find on Nexus Mods.
It looks like the main texture focus is for the stones and rocks in the game, which are improved greatly in some areas of the world. There have also been changes to some of the trees, wood crates, and ceramic roof tiles. It is currently the most endorsed mod for the game on the site and was last updated on Dec. 31, 2015. You can check out a video of the improvements brought by the mod here.