According to the December 12th Postal Bulletin, this stamp will be issued January 15th. However, the Bulletin has New York as the first-day; the correct city is San Francisco.
From my October preview:
2014 will be the Year of the Horse, but as with the other six stamps in this series by Kam Mak, the design shows artifacts associated with Lunar New Year celebrations, as well as peonies, traditional symbols of prosperity. In this case, it’s Chinese drums used by revelers to welcome the new year.
More details here as we get them.
We do have illustrations, though:
Added December 19th: The Digital Color Postmark design: 
From the USPS on December 17th:
Around the world, a new year is welcomed with noise! Chinese drums, with drumsticks painted red for luck, highlight the U.S. Postal Service’s 2014 Year of the Horse stamp, seventh in the Celebrating Lunar New Year series. The Year of the Horse begins on January 31, 2014, and ends on February 18, 2015.
Across many cultures, in the United States as elsewhere, the Lunar New Year is celebrated in various ways, often with parades and parties. Firecrackers are traditionally used to scare off evil spirits and welcome this time of renewed hope for the future. Lucky foods are eaten — kumquats, for example (issued in 2011) — and given as gifts. Festive lanterns, colored red for luck (issued in 2008), are common decorations at Lunar New Year celebrations, where they are frequently hung in rows.
Combining original artwork by Kam Mak with two elements from the previous series of Lunar New Year stamps — Clarence Lee’s intricate paper-cut design of a horse and the Chinese character for “Horse,” drawn in grass-style calligraphy by Lau Bun — art director Ethel Kessler has created a culturally rich stamp design that celebrates the diversity of the American experience.
The Year of the Horse stamp is being issued as a Forever® stamp in self-adhesive sheets of 12. Forever stamps are always equal in value to the current First-Class Mail® one-ounce rate.