An idea I've toyed with is having a housing NPC that you can challenge in your house.
You could give the NPC extra cards and from those cards make a deck for said NPC to use and make rules for them as well.
Players can then challenge the NPC to a game and see how they fair.
Alternatively, you can set the NPC up with several decks like in the portal app so to change it up.
A just for fun thing.