Usually, the back of the head is the most left or right part of the front of the head, they just circle the texture around the model, for example, the back of the head of your Vulpera should be right here.
Try using a program like paint or GIMP or even photoshop, modify the PNG file and see what happens when you place it on your model. If it's not there, then it is the top left part of the texture that you highlighted, so you just have to modify it instead.