OPTIFINE IS NEEDED!To get multiple textures for one mob, is more complicated than you may think, but if you pay attention, you should understand.
1: Make sure you have optifine or mcpatcher. If you do not have one of those it will not work.
2: Open your resource pack folder.

3: Open the pack you want than click assets.

You should now see a Minecraft folder, go ahead and open that.
4: Now, You should be in a folder that has different folders in it such as Textures. Look for one that says “mcpatcherâ€. If you do not have one with that name, create one by Right clicking an empty spot, go go to “New†and click “folderâ€. Now you should have a folder named “New Folderâ€. Now you want to double click it and delete “New folder†and put “mcpatcherâ€. Even if you are using optifine!

5: Now open that folder. If you already had that folder, you should have a folder called “mob†If not, create one just how we did in the other step. Once you have a mob folder open it.

6: So in the mod folder, you can create a folder or any type of mob you want to have multiple textures for. So if you want a ton of dog textures make a folder called “wolfâ€

7: The next step is important. You put the texture of the mob in this folder with .png at the end. So if I add a Wolf texture it would be wolf.png. And if you add multiple, you would add a number at the end. So another wolf would be “wolf2.png†then “wolf3.png†Also, with the wolf, there are three textures for it. There is wolf.png, wolf_tame.png, and wolf_angry.png. You will need to have a texture for each one.

8: the last step is Easy. Go into you minecraft Options, Then go to Video settings, than Quality, And on the left side, there is a thing thats says “Random Mobs†Turn that on otherwise it will not work. After all of that you are done
