In general, I recommend people print out and follow the optional checklist/instructions as a guide. That is what we did. We didn't even send any pictures, although we had evidence (passport stamps, primarily) of several years of trips back and forth between the US and NZ before filing.
That being said, for MENA/S. Asian countries, and particularly Iran, the general advice is to front-load that petition with as much high quality evidence as you have. This is because certain countries (Iran included) are high-risk/high-fraud, and there is additional vetting of visa applicants. You do not want to give them any reason to deny for lack of relationship evidence, as that is at least something you do have control over. The very best type of evidence is from time spent together in person - the more time, the better.
How much time have you spent together in person? Do you have any 'red flags'?