I have a few idea's. It's sorta like another card game. But any ways. Here are the card types:
Character: Pretty basic. They'd each get their own Attack and Defence and Health values.

Magic: This would be like Weapons, like you could equip the URJazzCC card with a Blaster power-up to double his attack. They could also include airboards for better defence (Like say add 500, but Seekers not included). Or Carrots to up your health 500. That sort of stuff.

Arenas: Some Characters would have advantages in different arena's. Like Jazz or Spaz cards.

Trap/defencive: You could have like say, the WARP card. It is only activated when one of you character cards is being attacked, and it warps them out of the way. Or The trigger Zone. It triggers a wall in front of you. Or Ricochet, which would reflect all attack back at attacking character.

Then the whole attack and defence and health thing could work like this. You take the attack of the attacking card, and subtract the defence of the card being attacked. The difference would be how much health a card would lose.

When there are no character cards out, you lose DIRECT HEALTH (Each player should have some health to start out with.) Magic cards should also effect their direct health. And when your character card is destroyed, you lose....Say.... 25% of their MAX health.

I could elaborate on this more, but I won't. I think making something like this would be pretty good. Any comments, opinions, or other ideas?