Some time ago I made a simple python script that allowed you to pack multiple images into the R, G, B and A channels of a texture. I used it when I was playing around with the default shader for Unity. I redid the script yesterday to allow for a bit more flexibility and just to make it more user friendly. Check out the video to see how it works. It uses Pillow to do all the image file operations, the script tries to download it using pip in case you don’t have it in your Python directories.
Download the project file here: channelscrambler