You can only either blackmail or not - you can't blackmail "a little"
... and of course the question is whether he had her consent to display this image, or is it simply another case of "revenge porn"?
<sigh> Whoosh.
Sorry if that was too complex for you
Lets break it down and make it as simple as possible.......
Did the artist have the consent of the female in question?
If she did not consent do you find he publication of the image acceptable or unacceptable?