Shirtless Pics: Qualifications

What would be the requirements for someone to benefit from a shirtless pic? I've been getting hung up on if I need to reach a certain BMI or if x amount of muscle groups must be visible enough. As an ectomorph, I am closer to my potential if I am judged by the latter as we may be naturally skinny, but don't have much body fat either. Currently I'm 158lbs and 6'0ft (21.4 BMI) after 1.5 years of consistent training. I believe I still have some room for improvement but I doubt I'm very far off.