I don't really mean EVERY card game expansions pack like for Call of Cthulhu or Game of Thrones, but it would be nice to be able to add Dunwich, Broodwar, Novgorod and the Isle of Dread to the collections feature.

Not only would it be fun to list these, but if I'm checking out someone else's list of games, I can tell if they have any of the expansions for a particualr game. Arkham and Runebound have several expansions each, and they do provide different gameplay experiences. But it would be someone odd to lisst all the different Runebound "decks," or the separate Wings of War sets, not to mention all the ccg/lcg expansions. But knowing if someone I'm discussing a game with does or does not have Innsmouth Horror can come in handy.

http://www.edgeent.com/v2/edge_tienda_resultados_wish.asp?etbus=Wish&ewid=18

It would also make the Wish List feature easier to implement.