Board Thread:General Mod Discussion/@comment-30303386-20170923221829/@comment-26553378-20170930130703

gimp is also nice freeware for it. beyond that get a resource pack creator so you can template off mod textures if you're stuck, its also helpful for figuring out what the dimensions of entity/armor wrap textures are (wrap textures are basically the net of an entity/armor skin if you are familiar with the term)