I'm very sorry to bump such an old topic, but I've finally modded on of the files to include all of the neutral symbols. Unfortunately, they replace other symbols. This shouldn't cause any problems in multiplayer games, other people that don't have the symbols should just see the normal ones.

To install, go to your Sins of a Solar Empire folder; then go into the textures folder and backup your old RaceLogos.tga, and then replace it with the one in the zip file. The zip file includes a short readme and the modified RaceLogos.tga.

The link for the file is:http://www.megaupload.com/?d=YLGOKWV5

Credit goes to Stardock for the artwork, I just made some changes.