threebuddies has found a way to install custom textures on Minecraft Pi Edition! Here’s his instructions:
HOW TO INSTALL
note: this will only update the terrain of MC, if you want you could place in the files from the textrue pack zip and place them into the correct folder in /home/pi/mcpi/data/images. There are no mobs in this edition of mc.
-download the texture pack into the default folder for downloads on the pi
-extract the .zip that you just downloaded, do this by right clicking and clicking on “extract here”
-navigate to /home/pi this is where the texture pack should of downloaded
-open up the folder “assets” and copy the terrain.png file in that folder
-navigate to /home/pi/mcpi/data/images in the file browser
-rename the terrain.png file in /home/pi/mcpi/data/images to terrainback.png this is a backup of the terrain.png
-Right click and paste the terrain.png file in to the /home/pi/mcpi/data/images folder
-Load up MC:PI and now you should be using the texture pack you just installed
And here’s an image showing the custom textures on a Pi!