Even if this topic looks a bit old, I can give you ideas that I can't do myself for the moment - I need more experience for that
There's my list :
charcaters from your favorite film/cartoon
unicorns
Creeper Priestess - actually I'm trying to do one but that's not a real success...
beautiful clothes you like, put together, plus a beautiful hairstyle, and you have a super cool skin !

Well, good luck ! Hope you'll see this

ok i have a really long list, but here are the main ones i really want

Front:Sugilite Back: Sardonyx

Front:Steven Back:Rose Quartz

Front:Garnet Left:sapphire Right: Ruby

These are all from Steven Universe so good luck XD

Ooh I got a good one for you it requires some brain power (yea I know your like "what?! This is impossible then!" But I believe in you!) (well that was weird..)
It is simple.. Half of the skin is some sort of creature of darkness and the other side is some sort of creature of light.
Good luck!