I think that people really underestimate fan art because it isn’t “professional”. There are a lot of people out there who do fan art and are very talented. The artists featured in this post are artists are from all over the world and all of them share their fan art on Deviant Art.
Click names for profile and artwork for imagery.
Ironman and Deadpool
The Incredible Hulk
Star Wars Saga
Jack Sparrow (Pirates of the Caribbean)
Jim Parsons (The Big Bang Theory)
Images © of their respective owners