Making Icon Mods

Does anyone know how to make a mod to replace unit icons? I am asking because a data mod I made caused all the new unit icons (encrypted in a different way from the older unit icons) not to show up when I ran the data mod. The new ones which don’t appear are the ones you can see the images for below.
I am hoping by having the icon mod (a graphic mod duplicating existing unit icons) will compel the game to show the icons correctly.