It is not possible anymore to upload photos for ships without MMSI, even if they have IMO. So, forget old ships or scrapped recently.
Also, if active vessels have sometimes hidden or unclear MMSI signal -the same not, just forget. And they are not going to improve it somehow as reported currently by their IT team. Hmm....
By this "progress" they one time to be faced to keep active vessels only. It is not good or bad for them since they operate an AIS system not a historic one, but users and photographers have to keep it in mind.