I know people are always looking for good diffusers, and I haven’t seen this one shared here, so I figured I’d share it.
I came across this translucent white cast acrylic on Ebay, which isn’t too expensive. I gave it a shot, and have to say, it is AWESOME if you are looking for something that will not show pixels through it. I tested it on a 16x16 matrix, but also think it would be really cool cut into thin strips to diffuse long LED strips.
Another interesting thought I had was that if you used the 1/4" variety (I used 1/8"), you could probably superglue the LEDs directly to the sheet, and get full diffusion with virtually no visible pixels. With the 1/8" sheet, you can see blurry pixels with it pressed against the acrylic, and offsetting it about 1/4" back from the sheet gives you a completely diffused look, so 1/4" thick sheet should diffuse it completely even when there is no separation.