I present here my firmware code: K.C. aka “Kacey” short from Keyboard Controller.
More info (about its features, motivation, uses etc.) on my website.
Also in gallery with pictures, and few videos (without comments though).
Key feature is the ability to edit any key mappings, layers, sequences/macros on display. Layout is also drawn on it. Plus it has few demos and a game
It works on a Teensy 3.1 or 3.2 board with a ST7735 display (160x128, 16bit color, 1.8" LCD).
Code is on github, with some info on used libraries and connections.
Should probably work with any matrix keyboard. NKRO is NOT implemented though, anti-ghosting is. Because I use it on regular ghosting matrix keyboards with foils (i.e. not mechanical).