In commemoration of the 20th anniversary, the ARISS team is planning to transmit a set of 12 SSTV images that capture the accomplishments of ARISS over that time.
While still to be scheduled, they anticipate the SSTV operation to occur around the weekend of July 15. This is now scheduled for Thursday, July 20 until Monday July 24 1800 UTC.
(I record the received audio and then later decode it using a program like MMSSTV)
An SSTV image sent from the ISS on Sunday 7/23/2017 around 10:00 PM Pacific. This was a visible pass of the ISS so it was easily tracked with the naked eye, making it easy to aim the antenna.