diffuser/mount for 5mm LED Grid Box

I really liked rantmakes' LED box but needed a mount and diffuser. My addition provides this at a basic level: it's not great, it's pretty enough but it works. The original box has space for 121 5mm LED's (I only used 120, I couldn't wrap my head around the last piece). I used cheap LED's wired in series in strings of 5 LED's, which was then wired in parallel (I think) to a 24v 5a wall wort (essentially). Each string has a 330ohm (1/4w) resistor on the end of it.
(Disclaimer: I'm probably wrong with my formulas and wiring, it works for me but figure out the correct numbers for yourself).

The mount and diffuser were designed to be as "exterior" as possible, as the original box doesn't leave a lot of room after my hack-job of soldering and glueing. After printing and processing, the original box/face were superglued to the base of the "light modifier" piece (see photos). The "light modifier" hugs the box just enough as long as the base is glued. I glued the diffuser into plac