You can't create community items (collectible cards, badges, wallpapers, etc) until you pass a certain threshold in sales. I think it's Valves way of ensuring people don't launch junk games purely for the collectibles.
It's always fun to finally get a chance to make them; a sign that the game has cleared its first hurdle, and is now considered a "real game" :)
The full set includes a badge, emoticons, 5 backgrounds and 11 collectible cards.
Hopefully I've caught most of the issues people have found since launch; thanks to everyone who's helped report bugs, give balancing feedback and played the game. I still need to follow up on the Eternal Flame achievement, since that seems to not trigger for some people.
Hope you've all enjoyed playing the game; I've certainly enjoyed making it.