So you have a Teensy and a RGB LED Matrix Panel and you want an easy way to add graphics to your matrix without having to toss aside your Teensy or do too much soldering. Enter the SmartMatrix SD Shield v3 - for Teensy 3.1, 3.2 (not the Teensy LC)!
The example sketches included with the SmartMatrix Library will get you started quickly displaying graphics, patterns, or even animated GIFs from a microSD card on your panel.
The shield brings the 13 I/O signals needed to drive the panel out to a connector that matches the pinout on the panel, and brings the rest of the I/O signals out to convenient expansion headers. The board includes pre-soldered 5V level shifters and a microSD card slot.
It's a great board for easily expanding your Teensy's capabilities. Comes as a kit of components, but the small parts are soldered already, leaving fairly easy to solder through-hole components. You'll also need to program in your Teensy with the SmartMatrix code available on the project website.