I appreciate @pelson has a preference for adding it to the ```images``` attribute (I can't find any documentation on this, but there is a ```get_images()``` method) as it means the images get drawn with the others (e.g. those added via imshow), but ```add_artist``` has some benefits too, namely that it calls ```set_axes()``` for you. Ideally there would be an ```add_image()``` method we could use, but in its absence I'd favour ```add_artist``` provided it doesn't lead to any unexpected drawing order issues.