How to force snake tail In Snake game to show the texture that is correct for it

I am making a snake game in unity. The Game is very simple, it uses texture2D to display head, tail, and body parts. Now I am stuck in a problem. For the head part I stored 4 textures(each one is for one of the four directions) and 4 for Tail. I check direction and in onGUI I select the appropriate image for the snake head and snake displays correctly but the problem is, It is not working correctly for the tail Image.