Looking into the article and situation, the mayor has never claimed explicitly that the measure is designed to increase diversity, though that is a separate goal of his.
The photo of the applicant is so the rest of the department, including him, can familiarize themselves with their coworkers, as mayor Adams stated it is disrespectful to not know who you are working with, and that he wants to get to know his departments.
The people asked about it believe that not only is it part of mayor Adams' goal to have the departments match their constituents, that it would increase workload processing/finding the photos as the person putting in the application isn't necessarily the one providing the photo so people will have to hunt through socials, and that they should just hire anyone qualified because they are currently understaffed.
Now, if it is purely a move to increase individual recognition as stated, that's fine, but likely would be better handled differently (provide a picture when hired/get one taken to make it so people don't have to waste time hunting down photos, that sort of thing). If it is to reach racial quotas, I'm less ambivalent about it, especially considering they are understaffed. Just get qualified folks to work the city. Hell, I'm of the opinion to not have much information about the applicant be known in general, race, gender, appearance, etc. to weed out biases anyway, keeping things mostly merit based.