Well, we could think of a list of conditions for each medal individually. We should also have different ones for Empire and Alliance.
Some conditions could be:
-Defeat a fleet larger than yours
-Capture a planet single-handed
-Destroy a certain number of enemy ships
-Fight in a certain number of battles
-Reach a certain total fleet count
-Fleet admirals should get a "marshal's baton"
Empire medals could be based on German decorations with slight changes (
Order of the Black Eagle,
House Order of Hohenzollern, etc.) , and Alliance ones could be based one American ones (
Medal of Honor,
Legion of Merit, etc.).
We could use existing images from Google images or something for them. Searching "fictional medals".