If you want to make a icon / square of a skin be different than the default, without changing the default icon (because if you wanna add new tab icon/square like Kayn used to have on his skins)
Note: This apply to every champion, I used Yasuo as a example
You can extract the default square (to use as a base image), then edit, and change the name to be a separated icon to the skin.
After that you setup the skinX.bin to a different path, is on the start of the skinx bin, and is super simple.
Also, dont forget to uncheck the “Remove Unkown” when adding the wad in LCS
Final Result: The enemy yasuo didnt have the skin, so, didnt have a edited icon (this apply if the yasuo is on you/are in your team too)