Steam Winter Sale trading cards have recently started dropping. The event is expected to start on December 18.
Entrepreneurs have already started putting ordinary and foil trading cards up for sale on the Steam marketplace.
Currently, Steam trading cards can be obtained for creating profile badges. During the sale itself, they will also be given out for every ~$10 spent in the store.
The cards are currently "secret", but Valve will reveal the design of this year's collection when the event starts.