you mean how to have the same texture on the other side of the plane?
Well, there are many ways, for example, you could put both images on the same image file but on oposite ends (i.e. one on top and one on the bottom), or you could cut the surface in half and texture each one separately using the same picture, or you could use a layered texture to attach that same file twice (once right where it is, and the other time rotated and placed in a different position.); that's just what I can think of right now.