I've laser-cut the rear panel with engraving for I/O and a handy GPIO pin-out for the TTL DB9 output. I thought since I've got 6 spare pins I might as well connect them to the Pi GPIO for use with external projects. The engraving is filled with acrylic paint using a sort of silk-screening technique.

Here's a teaser GIF of me running cool-retro-term on Arch :):

I'm only awaiting the dual USB panel mount from China before I can complete the build. In the meantime, I'm comtemplating adding battery power...