Additionally, I noticed that the spot cards all have a little circle in the center background. I would remove this - since all the art is monochrome, it's easily confused as an extra pip by someone not paying enough attention.
Consider making a tier for "two and two" - two deck of each of the two designs, or four decks of one if you fail to reach goal... Speaking of which...
You could be setting yourself up for a problem down the road. Let's say you get to your goal and the project is winding down. If it becomes clear based on analytics that you WON'T reach the stretch goal for the second deck, you might find backers who backed based on the assumption that the second deck would be made dropping their pledges to a reduced level. For example, the guy who pledges for the half-brick expecting to get three of each deck might not want to have six of the same deck, and would drop his pledge to the three-deck tier.
Summed up, it could result in reaching your goal, only to drop below it in the latter days of the campaign.
It would have been better to make the second deck strictly an add-on for all the tiers. Then you wouldn't get backers who back based on an assumption potentially putting the project in jeopardy.