PMC allows for feedback and "diamonds" (likes). Looking at the work of top-tier skinners can provide inspiration for improving your own shading techniques.
Planet Minecraft is widely considered the gold standard for community content because of its structured submission system. Unlike other repositories, PMC features a that allows users to paint and preview their designs in 3D directly in their browser. planetminecraft.com-skin
Modern Minecraft skins have an "Outer Layer" or "Overlay." Use this for hair, hats, or accessories to create a 3D effect. PMC allows for feedback and "diamonds" (likes)
Once finished, you can save the skin as a .png file to your computer. planetminecraft.com-skin