Things like a map (so the player has some control over events), items that only serve to buff other items, and modifiers to specific cards, are a traditional staple of games like this. Don't worry about being "generic" because this game is fundamentally pretty unique.
oh, also:
- please consider Mac portability long-term thank you
- "cripple" could offend somebody idk
That's my two cents spent, I won't suggest anything more except for bug fixes. Again, ditto on the "truly awesome and addictive."