It would be nice to be able to trade them. I had happened to glance down at my score the other day before I received a valuable. It appeared as though I immediately got the worth of the item at the time I received it. Of course, the old eyes are not what they used to be, so I could be wrong! I have acquired a few cards from skeletons too, however, like you say they are all pretty small cards. Cheat? Who me? A pirate!
See you in the game!