You cannot position the image to be used in a window's background, however you could workaround this by editing the image in MsPaint or an image editor of your choice and creating some white space (or whatever color your current background is) around the image, resulting in it being tucked away in the bottom corner. Then include the "f" switch in your /background command to fill the window with the supplied image. Check out /help /background for a list of other available switches
