This is a simple case, stand, and Raspberry Pi mount for the Adafruit 64x64 RGB LED Matrix with a pitch of 2.5mm.

This stand is designed with a slight lean-back angle so that it can be placed on a table and easily viewed from most angles.

I designed this myself because I was unable to find anything pre-designed for my matrix type that satisfied the simple/sleek and minimalistic look that I was interested in.

Raspberry Pi
The mount that attaches to the back of the matrix is designed to fit the dimensions of a Raspberry Pi 3 B V1.2
It may fit other similar Pi models but I'm not confident on which ones (data on this was hard to find).

Known Design Issue:
When the Raspberry Pi 3 is mounted with the included mount, it fits snuggly at the back of the matrix. However, many of the USB I/O ports are blocked by the rest of the case, and I believe only one remains usable.

Printing the Matrix Grid
The grid was the most difficult piece of this project by far. It couldn't be designed in CAD and printed because the slicer had trouble with it and wanted to take ~2 days in total to print it...

I ended up following the advice of a @nlapenn_222745 on Printables which involved creating a 162.5mm x 162.5mm x 5mm box that matches the dimensions of the matrix (results in 64 by 64 grid), and then using slicer settings and infill to get the desired grid.
In my testing of this, I determined that printing the grid this way worked but the edge matrix columns ended up with a bit of extra PLA material that didn't make them uniform. This was not good enough for the perfectionist in me...
So I created a similar box but with slightly larger dimensions (165mm x 165mm x 5mm) to fit an extra column on each edge (resulting in a 66 x 66 grid) that I would then cut off. This proved to be a bit of a hassle but worth it in the end for a nice final product (See "Post Printing" "Matrix Grid" section for details).

Diffusion & Glazing
For diffusion and a finishing photo frame style look, I chose to use a single sheet of parchment paper and a thin sheet of clear acrylic that I cut to size.
The size to cut for these pieces is about 170mm x 170mm.
The actual gap designed was 171mm x 171mm but it's best to leave a little extra wiggle room to ensure a good fit.
Diffusion: Parchment paper (1 sheet)
Glazing: Acrylic sheet (no more than 2.5mm thick)

Notes: I tried a few different types of diffusion and found the parchment paper works best. Regular printer paper was a bit too opaque and made the matrix difficult to see during the daytime. Wax paper was good for viewing in the daytime but it was very flimsy and didn't work as well for off-angle viewing. Parchment paper was a nice middle ground.

Stands
The stands are included in separate STL files and are labelled 'left' for the one that goes on the left and 'right' for the one that goes on the right (when looking at the back of the matrix case).
The holes that are in these stands are oval-shaped to ensure that there is flexibility when screwing in the M3 screws to the back of the matrix display and through the casing holes. This ensures that the case and stands can line up as perfectly as possible.

There are cutouts in the base of each stand that I initially intended for tungsten cube weights. However, the stands function perfectly well without them, so the weights are optional.