Minecraft wiki entry for Creating_a_resource_pack, associated text: To add textures or custom models, it is suggested to use a modeling program that allows for a visual-based editing system. Like with audio conversion websites, there are many online tools, though a common recommended program is Blockbench. Most image editors will suffice to modify textures, but it is recommended to use an editor that supports transparency such as paint.net or https://pixlr.com/ so that you may add transparent pixels to textures.