Here's an idea for jam 3: an art battle for cards without a picture. Make a topic on the forums and have people post their pictureless/artless cards there. Each round then goes like this:

1.present a pictureless card from the submissions.

2.people make art for the presented card.

3.the presented card's creator chooses the winner.

Repeat until all submissions are used or most people become tired of it.

The submission thing is used so people can compile the artless cards together and to double as an announcement post.