Just go to the texture room and add a texture to the color channel. This should place the image on the plane stretched to fit. If you only see half of it, set it to tile twice and that should tile it across the front and back. An infinite plane will HEAVILY distort your image when it's displayed, because C will try to stretch the image over an infinite plane. UGLY! A plane is the size you make it and will not overly distort your tracing image. If you insert a plane with the tool, instead of using the menu, and then click in the side view, it will place it perpendicular to your view. I.E. on it's side vertically. Or you can also, like Kix said, rotate it numerically with the properties tray. Hope this helps!