Now that you say it, I believe you're right. I was focused on getting rid of them, not making them.

Which means that I accidentally fell prey to a piece of trivia that I love. Which is that if you create a set of cards with impossible suits, people flipping through the cards will confidently recognize them as a similar possible suit. It is only when presented slowly that people will learn to see the impossible suits, and this process can be difficult. (This example is presented in Thomas Kuhn's The Structure of Scientific Revolutions.) So when I remembered that it looked like something you'd see on a card, I remembered the color but then substituted in a possible suit for the shape.

Silly me.