How should I improve my skin making?

[Oak]

They may not fit right with 2DWorlds avatar format and size, but they are ok nevertheless.

But he just copied them. He didn't recreate anything, he just took it straight from the source.

Not really, his skins are just highly influenced from other games or site sources. He always tends to re-model things which is fine. Face it, he is the best. Some of the stuff he makes is 100% original but most isn't; it's okay though.