I understand the aversion of voting for propaganda -- I've seen how it was abused in the past. On the other hand, I also see the point, that some teams put a lot more effort to produce something nice, entertaining and fun and it feels fair that they shoul dbe rewarded more than those who choose the easy way to create a post with minimal effort.
I would suggest a system, where propaganda can earn upto X cards -- decided and awarded by the WMs, not by public voting. So if it was decided that propaganda can earn upto 10 cards, then when the deadline for propaganda is reached, the WMs would discuss and award some cards to each team, e.g. 0 card for not submitting anything, a few cards for easy-out humorous posts and 8-10 cards for involved, interesting submissions. It wouldn't need to be a full ordering, multiple teems could get 10 cards if they submitted very nice work.