I Couldn't Get It To Work Until...
...I added this texture in a my baseq2 folder. Maybe this is because I use Yamagi Quake II, but in case anyone else runs into the same issue, I found that texture here:
I set it up in folders as textures/e2u3/metal22_2.wal inside baseq2 and then everything was smooth sailing!
As far as the map goes, it was pretty cool! Good use of reusing areas throughout the game and the end battle was neat (once I figured it out). A couple of places I got stuck on the geometry, but I just noclipped out of it. For a map made in "a few hours of spare time," I thought it was quite good. The song looped a lot, but I figured I just am slow at Q2. Definitely worth checking out!