Some say the best angle for a great dick pic is from the underside, meaning the side facing away from you. Be sure to leave your balls out of the frame.
Since the dawn of catcalling, men have operated on the delusion that aggressive and unsolicited advances are somehow desirable, despite drastically low success rates. Perhaps unsolicited dick pics fall into this general category of too much confidence and too little awareness. In short: get consent!
When you're engaging in consensual sexting, dick pics can work. Use proper lighting, capture the best angles, and leave your balls out of the frame to render the right impression.