The image should indeed be a .png, but you'll also want to make sure you're using the correct mane mask. In your texture folders there should be a mane mask that looks like a black square with a few upside down triangles sticking out on the bottom, and a transparent area around those triangles. You want to lock the transparency on that mask so you can only color where it is black. It's important that the transparency around the black area stay transparent. Then save that as a .png. If you have already done this, then you might have a issue with your image corresponding to your code.
Its very important that your image name is exactly the same as what is written next to the texture part of your code. So for example, if your code says:
texture preset_9mane.png
Then your image must be: preset_9mane.png, otherwise it won't work.
Also make sure this part of the code at the top reads:
material preset_9_maneMat