I’m wanting to give players the ability to use custom texture packs they make in my 2D top down RPG.
I particularly want to do it the way Minecraft did it, in which they just enable the pack, and the game will replace all the default textures and animations with the ones the pack contains.
1 Is it possible to do this in Unity?
2 If so, how can I?
I would really appreciate some insight into adding this to the game. 
Yes, everything is possible in Unity3D.
You can use texture loading functions in the Texture2D class to stand up textures from external data.
From there you just need to get all the right textures into all the right Material slots in your game and you’re done.
Thank you very much for replying! Tough how are animations (like player running) affected by this? And how can the game automatically replace textures with ones in the right folders with the same names?
You can find out for yourself by writing a little bit of code to swap out one texture in whatever setup you have.
That should take about 5 to ten minutes tops of coding and setup and you will instantly see how whatever system of animation and display you use operates when you swap out the graphics.
Thank you, I will give that a shot!