I’ve been trying to do this, but have not had any success so far. Thanks for your help!
The image will resize to fit the square, so adding space around it before importing could do the trick. But in most cases it makes more sense to use a graph background, add the image there, position it how you want, and remove the axes and gridlines.
@JayChow - fantastic, thank you for your help. Looks like your second suggestion did the trick!