You changed the color of the default shader, lambert one. You're supposed to create a new texture first and apply the picture on that. Restore lambert 1's color back to the greyish color, and put your photo on a new texture.
"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man."
George Bernard Shaw - Man and Superman