Randomized Minecraft mob textures!!

For my mod I want to make my mob fully random every time one spawns. Right now I’m making the visual appearance of the mob randomized.

Basically I have a 600x600px png with different colors and patterns, and when rendering the mob I make the code pick a random point on the large png to use for the texture net.

Every time I close and rerun the project, the mob looks a little different! Here are some combinations below. Next I wanna make it randomize every time one spawns.