What is the ruling on and punishment for one who views nude pictures?

Allah commanded believing men and women to lower their gaze. Whoever fails to do so has disobeyed Allah's command and exposed themselves to negative consequences, including: the loss of the blessing of sight, because they did not show gratitude for it by using it in a way that pleases Allah; falling into indecency; darkness of the heart; incurring Allah's wrath; and committing other sins. These harms include punishment for those who view forbidden images, in addition to the torment of the Hereafter if Allah does not forgive them.