Most games in the genre seem to have this, and it would be especially useful in Transcendence. It could be based on size (length) and/or mass, with appropriate thresholds. Two categories, gunships and capital ships, would be good enough, but dividing each of those into light and heavy sizes might also be nice. The icon for small stations might need to be changed to a different shape to avoid confusion. Also, particularly large stations could get a larger icon, too.