Hello Lightshipfan,
I don't have any lighthship postcards but I can share some pictures I took of a lightship a couple of weeks ago in Rotterdam, Netherlands.
This lightship is anchored in the canal by the Rotterdam Maritime Museum. The name on the lightship says: 't Lichtschip Bar Brasserie, Breeveertien.
I don't have any information about the lightship but thought you might like seeing these photos.
BTW...I thought cruising through the Kiel Canal between Germany and Denmark on a cruise ship was spectacular!