Slow Scan TV (SSTV)
Slow-scan television (SSTV) is a picture transmission method, used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or color. More from the wiki here.
Here’s an SSTV Cat scan in action
here is a bank of slow scan images
the “ultimate” slow scan tv website
slow scan tv broadcast from the international space station
A list of SSTV softwares avalible
install on a raspberry pi by typing into terminal “sudo apt-get install qsstv”