This 20-stamp issue was announced as part of the USPS celebration of its 
semiquincentennial. According to the April 28th press release, the design
by cartoonist Chris Ware that invites the public to spot a fun array of familiar postal items and icons while following a mail carrier on her rounds through four seasons of the year.
The USPS says this issue will be released in July. Further information will be posted below the line, with the most recent near the top.
Here is a look at the design of the rear of the pane of 20:
