Here is about the amount each part of a skin matters in making it good (I chose these percentages based on my experience on PMC)

Shading how well-made the skin is- 35%
Originality- 60%
title- 5%

Originality is very important in good skins. If there are a lot of the same skin out there, it is not original. If there is more than 5 of the same titled skin out there, it will not be credited very highly for originality. You need to get ideas that nobody else had. It's not hard. How do you think of original skin designs? 

Your brain will not be able to generate an idea that is not based off something you haven't seen. Your brain only knows from experience whether it's hearing, reading, kinesthetically learning, or another. Your brain can create imaginary things only based on what you  know. A mix of different things you know, mixed together to create something of imagination. To think of original skin ideas, you need to mix together things you know and create ideas. After the first few skins you made, it most likely got harder and harder to think of ideas. You had already used most of your knowledge to mix and create skins. To make original skin ideas, you need knowledge. Go outside and study some birds and insects. See a beautiful butterfly? Make a skin of it. Alter it with your other knowledge, and create something of your own imagination. The more knowledge of experience you have, the easier it will be to think of skin ideas. Are you looking for ideas right now? Walk around and look at everything around you. Do you see something akward or something you could make a skin out of? Is there a phone near you? Why not make a girl with a dress on that has a big phone drawn on it. Look around. Learn from experience. Think about your life and everything you've ever seen and done. Ideas will flourish.

Asking people for ideas, looking up ideas on the internet, making your own skin based on a skin idea someone else had, are all what you shouldn't do for most originality. But you can think of ideas if you just try.

Hope this was helpful. Please like and share so more people can have this knowledge.