The scripts works OK for Maya 2018.3 but I got few notes:
-once I excute it , it gives me this error ((# Warning: The -bs/-borderStyle flag is obsolete and should not be used. # ))
-the script can be turned off then load it again & it remembers the images you added to the scene, thats Good.
-the button "Select" wokded for me only if I am in another viewport that I didnt use to creat the plane ((if I created plane for Persp, if I got oFront view for example then press (Select), it will change it from Front to Persp & frame it to the size of the image.
-"Look Through" button didnt work for me at all in any case (whatever I choose camera or even plane itself, when I press it, nothing happens)
-All other features worked very well :)