The Trading Cards (and all the little fiddly things that go along with them, like emoticons and backgrounds) are just about ready to go! Right now we're just waiting to pass the sales threshold that enables us to activate them. Once that happens, I'll push the big button, and the Trading Cards will flow!
For more on the sales threshold, please read Valve's blog post about it here: https://steamcommunity.com/games/593110/announcements/detail/1954971077935370845