How do I make a resource pack for IC2?

If you can make a resource pack for vanilla minecraft, then doing the same for mods will be easy.

https://minecraft.gamepedia.co…/Creating_a_resource_pack

You have your resource pack zip name (resource pack name). In there you have a pack.mcmeta file. In there you write this:

{
   "pack": {
      "pack_format": 3,
      "description": "resource pack name"
   }
}

and save it. in that folder. Next you make a new folder called assets. In that folder, you add your custom content for vanilla minecraft and mods.

Now open your IC2Classic 1.12-1.5.5 .jar and you should see an assetsfolder and inside that you find an ic2 folder with all the sounds and textures that you might want to change.

Now you can begin to change textures that you want:

Inside your resource pack's assets folder, your map structure should be the same as in the assets folder in the IC2 Classic .jar. So it should look like:

Resource pack name.zip/assets/ic2/textures

And any subfolders such as sprites or models should be put in that textures folder. Then you can put your custom texture files (in .pngformat) and with exactly the same name as the ones you want to replace in those folders.

Then save your .zip file and move it to your resources folder and enable it in game.