Reflecting/Refracting an imageplane:

Select the imageplane (get it in the Attribute Editor)
-the easiest way is usually to select the camera, and go through the same way as you created it.
-or go into component mode and select 'Image Planes' under the '?' now you can select it in the viewport.

Under it's 'Render Stats' turn on 'Visible in reflections' and/or 'Visible in refractions'