Currently, work is on the randomize.py file. Go into point_mass.xml, and add as many textures as necessary in, making sure to label them with different names. They should be similar to <texture name="sample" type="cube" file="{}"/>, with the {} denoting that it is open to randomization. (This was implemented with Python string formatting; you could use {1}, {2} etc. to have a different order when the paths are provided).
Next, go into randomize.py and update the _TEXTUREPATHS with filepaths to the PNGs to use. The format should be a nested list of arrays, where each array provides a list of possible textures to be used at the texture. For example:
[
["dog.png", "cat.png"],
["carpet.png", "marble.png"]
]In the above example, the first texture will choose between the dog and cat PNGs, while the second texture will choose between the carpet and marble PNGs. (These are chosen equally randomly, though this can be customized).