I must be going blind. I looked at that page before, but didn't recognize it
.
Now, the warships are pretty obvious as to which is the secondary image. (Destroyer Heavy <- Destroyer)
The fancier images I'm not sure about, though; what chain should I use for the SM barge?
I'm thinking: Barge ->, colonyship large, resourceship, baseship, dreadnaught, ..., escort.
The other thing is the one end-of-the-line default image.
If there are no ship images, we should at least require a racial picture, (which is the secondary choice for infantry), and I could build up a shipset of that.