Nocturne is a fun set, but isn't great for physical card storage. I think Night cards are the best mechanic to include if you want a new mechanic but are limited in storage space, as most of them don't require any extra piles (or at least, fewer of them require extra piles than with other mechanics in that expansion). Exorcist requires all three Spirits, Devil's Workshop requires just one of the Spirits (Imp), and Vampire requires Bat and Hexes (which Werewolf also requires). Other than that, I think there are 8 or 9 Night cards which don't require you to store any extra piles.