After you feel the factions and ships work there are many other tags that could be added.
BG
FG
Portraits
Logos
MODS (made into many catagoties from custom change to total conversion)
Save games (A way to make a Play By Steam round robin type of game for those that schedules do not allow Multi and do not mind taking a year to play a game.
In some expansion or DLC could add ability to save or load a game directly from this folder.)
Maps
I am sure there are others.