There is a variable called IMAGEFRAME that will allow you to turn on and off the frames of an image inserted and allow you to resize it with grips.
Check out HELP for all the modes available and the explanation of them. You will want to turn off the frame at plotting time probably so a setting of 2 (IIRC) should work for you. It shows the imageframe and allows manipulation but does not print it.
HTH
Regards,
DJ