So i know how to mod a formable its just that i have no clue how to make a image for it. If anybody that knows how to make a image like in the base game i'd like to know what software you are using and you are using as a base image.

Example of what im trying to make:

Sorry for the bad image

I believe most people will just use GIMP, Photoshop, Paint.net, or similar.

Then get a greyscale map (so it looks like the non-core states), and then draw over the states they wish to show as cores. Then crop out the relevant bit of the image, and use that.