In vehiclesize.txt of your mod:
Code:
Name := SuperMegaShip
Short Name := Supermega
Description :=
Code := SMS
Primary Bitmap Name := Ship_picture_name_1
Alternate Bitmap Name := Worldship (for example)
Vehicle Type := Ship
Tonnage := 100000
...etc
Name := UberGigaShip
Short Name := Ubergiga
Description :=
Code := UGS
Primary Bitmap Name := Ship_picture_name_2
Alternate Bitmap Name := Dreadnought
Vehicle Type := Ship
Tonnage := 100000
...etc
Here, the Ship_picture_name_1.bmp and Ship_picture_name_2.bmp are images of ships you'd like to use.