I like your work and your display! The voice sounds pretty good too!
What is the distance between LEDs on the display? I am thinking about making one similar but, I need to know how far apart to put the LEDs to make it look nice like yours.
I'm not sure about distance (probably around 2 mm), I'm actually using premade 32x16 bicolor board from Sure electronics (DE-DP14112). It has 8 3mm 8x8 Green-Red LED matrices and driven by HT1632c ICs so it needs just 4 wires to connect to arduino (plus 2 for power supply). Previously I tried making display with other 8x8 LED matrices but it proved a little challenging to drive them. You can build your own and drive it with MAX7219 (2 per matrix) if you are good with PCB making. Those LED matrices arrange nicely, just put them back to back (most of them have grooves that allows them to arranged tightly next to each other, almost like lego). I think it's more practical to use 8x8 LED matrices rather than making your own from separate LEDs, but of course it's up to you
Bicolor 8x8 can be found for as low as $1 each on eBay, and 32x16 display costs a little over $30.
Sure's matricies in DE-DP14112 are also much smaller than other 3mm 8x8 I was able to find. I don't know if it's good or bad, it will give you more DPI resolution, but smaller display overall...
But if you are planning