This version of the ESP8266 RGB Matrix that consists of two boards joined together with a cable. My first version used a NodeMCU along with way too many jumper wires. This version uses one five pin cable and a larger pair to power the matrix.
Check out http://www.instructables.com/id/RGB-LED-Matrix-With-an-ESP8266/ for all the details like wire diagram and Arduino library.
Check out the Files under the PCB directory for a parts list, schematic and gerber files to make your own.
To see a video of the basic assembly check out: https://youtu.be/_pmtngvNnLo
Special thanks to @witnessmenow for the inspiration and well documented instructions that helped me with this project and @pdp7 for the beautiful OshPark PCBs!