Ryman: Dressing up ANYONE as ME is always a great idea!
Jokes aside, just start thinking and the thoughts will lead you to ideas. One of these trains lad to my idea that the Aztec calendar was a warning of an alien invasion so the one scientist guy who figured it out built a robot girl to fight them.
See? Scour the internet, start thinking, play games: anything that gets you thinking.
You are not going to become popular overnight just because you do fanart from popular shows, don't even waste your time with that, lots of people are doing what's popular already and not all of them are popular. Better work on improving your art.