With apologies to Herman's Hermits.
I always play with map contacts on, and when you zoom in on the gray silhouettes from a radar contact, you get a fair idea of ship types from the silhouettes. Recently I started adding minesweepers (NMS_NO13) in the mission editor, and instead of the silhouette of a destroyer it has the same silhouette as a merchant ship. Like most minesweepers in WWII this one is a converted destroyer, got guns and depth charge racks and active sonar, so it should have the same silhouette as a destroyer.
Anyone know where the map silhouettes are defined?