I realize that when posting Airport photos you cannot use the ICAO identifier for US airports. However you can use either for aircraft photos and they will still appear on the airport page listed as both.
But with airport DCM, this does not work. Typing in "KDCM" brings no results on the upload page. Only "DCM" works. I checked and it is assigned the ICAO identifier "KDCM". It must be a bug.