I personally prefer to organize my photos both on the site and on my computer by ICAO identifier. With Aircraft Photos I can post them as either ICAO or IATA and they will show up on the airport listing. With airport photos I notice that there is now a drop down search suggestion feature like there is for airports. When I post them as K***, they show up in the search suggestions, but do not show up on the airport page which is still only search able by IATA or FAA identifier. If I post airport photos by IATA they will show up. This problem has existed before, back when there was no search suggestion menu for airport photos.
Posting Airport Photos with ICAO identifier