Think about things you like for skins, like certain colors or movies or video games, I've noticed you've already made a soccer skin. And as for shading, there are many amazing blogs about how to shade.

AND another thing, I like shopping online, so when I see clothes/cosplay I like, it makes me want to make a skin. I don't finish most of the skins I make, therefore I don't post them, but maybe this will work for you.

ALSSSOO do contests, even if you aren't competitive. PMC pretty much hands you ideas when they hold skin contests.

Well stranger, The most basic thing when it comes to skins, assuming you haven't already, is make numerous variations of yourself. I've posted two or so since I joined a few months ago, but usually I'm making skins for people who are part of the server I help manage (if you want, I could give you the ip, provided you're not a troublemaker). You could also try testing come color and shading techniques and posting them for a bit of critique. Hope this helps o: