What is the ruling of Islamic law on marketing products that feature images of unveiled women or shirtless men, with the possibility of directing the visitor directly to the payment page, or with very small thumbnail images, or with videos that contain images of unveiled women?

This was to distinguish between what is lawful and unlawful. As for piety, caution, and avoidance, they have no specific limit, and may even require abandoning this field entirely. So, fear Allah and avoid ambiguities as much as you can, unless that leads you to hardship, difficulty, and distress.