Use a dedicated pixel art editor like GIMP (free) or Photoshop (paid) with a Minecraft skin plugin.
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Using a 64x64 PNG, you can create the illusion of wearing modded armor. By carefully drawing chainmail or leather armor textures onto the overlay layer, your character will look armored even without equipping items. minecraft skin 64x64 png
Creating a skin that looks good in-game requires more than artistic talent. You need pixel logic. Use a dedicated pixel art editor like GIMP