If you want to move beyond downloading pre-made skins, you can use specialized web tools to create a custom 64x64 PNG.
Tools like Skin Editor 3D for mobile or the Tynker Minecraft Resource Editor offer precise control over every pixel.
To master the "Minecraft skin 64x64 PNG," you must understand the map. The flat image isn't random; it is a precise grid. A 64x64 template is divided into two vertical halves: