After making this video I realized I had forgetten one important step. Packaging it. At the end you'll see how I brought up that terminal that was in snowballz/maps/, you will need to run:
$ python package.py smallcrystalrush
To package it. Then it will show up in the game menus and be playable.
After testing out the map there were a few messups that I fixed afterwards, but you get the idea of how it's done.
You can download the two pallets I used - just unzip it in your gimp directory (for me it's /home/joey/.gimp-2.2/palettes/ which is where you would want to unzip it).