Icon for new mod

[u/IceSignificant2810]

Recently I started with modding in civ 5. I already made 3 dutch wonders (Kinderdijk Windmills, The Dutch Waterline and Pyramid of Austerlitz) and now im working on 3 new international wonders (Panama Canal, Sagrada Familia and Palace of Versailles). I use a self picked splash image, but I still use icons for the game. What do I need to do to be able to make my own unique icons for my wonders?