From the USPS:

On February February 22, 2014, in Mesa, Arizona, the U.S. Postal Service® will issue the Wedding Cake, 70-cent definitive stamp, in one design in a pressure-sensitive adhesive (PSA) pane of 20 stamps (Item 587500).

The stamp will go on sale nationwide February 22, 2014.

The Wedding Cake issuance, first introduced in 2009 and sold at the two-ounce stamp rate, accommodates the heavier weight of an invitation, as well as other mailings such as oversize cards or small gifts that require extra postage. The stamp art features a photograph taken by Renee´ Comet of a three-tier wedding cake topped with white flowers. Art director Ethel Kessler designed the stamp.

Item 587500, 70-cent Wedding Stamp Definitive PSA Pane of 20 Stamps

How to Order the First-Day-of-Issue Postmark:

Customers have 60 days to obtain the first-day-of-issue postmark by mail. They may purchase new stamps at their local Post Office™, at The Postal Store® website at www.usps.com/shop, or by calling 800-STAMP-24. They should affix the stamps to envelopes of their choice, address the envelopes (to themselves or others), and place them in a larger envelope addressed to:

Wedding Cake Stamp
Postmaster
Main Post Office
135 N Center Street
Mesa, AZ 85201-9998

After applying the first-day-of-issue postmark, the Postal Service will return the envelopes through the mail. There is no charge for the postmark up to a quantity of 50. For more than 50, customers have to pay five cents each. All orders must be postmarked by April 23, 2014.

here are five philatelic products available for this stamp issue:

587510*, Keepsake (Pane & DCP Set), $15.95
587516*, First-Day Cover, $1.14.
587521*, Digital Color Postmark, $1.85.
587531*, Stamp Deck Card, $0.95.
587532*, Stamp Deck Card w/DCP, $2.20.

Technical Specifications:
Issue: Wedding Cake
Item Number: 587500
Denomination & Type of Issue: 70-cent Definitive
Format: Pane of 20 (1 design)
Series: Weddings
Issue Date & City: February 22, 2014, Mesa, AZ 85201
Art Director: Ethel Kessler, Bethesda, MD
Designer: Ethel Kessler, Bethesda, MD
Typographer: Ethel Kessler, Bethesda, MD
Photographer: Renee Comet, Washington, DC
Modeler: Donald Woo
Manufacturing Process: Offset/Microprint “USPS”
Engraver: N/A
Printer: Banknote Corporation of America, Inc./SSP
Printed at: Browns Summit, NC
Press Type: Alprinta, 74
Stamps per Pane: 20
Print Quantity: 30 million stamps
Paper Type: Phosphor Tagged, Overall
Adhesive Type: Pressure-sensitive
Processed at: Banknote Corporation of America, Browns Summit, NC
Stamp Orientation: Vertical
Image Area (w x h): .7553 x .8667 in./19.18 x 22.01 mm
Stamp Size (w x h): .91 x 1.19 in./23.11 x 30.22 mm
Pane Size (w x h): 5.425 x 5.635 in./137.80 x 143.13 mm
Colors: Cyan, Magenta, Yellow, Black, PMS 874, PMS 9 (Warm Gray)
Plate Size: 200 stamps per revolution
Plate Numbers: “S” followed by six (6) single digits
Marginal Markings:
Front: Plate numbers in four corners of pane
Back: © 2008 USPS ● USPS logo ● Plate position diagram ● Barcode (587500) In upper right and lower left hand corners of pane ● Promotional text