Fan Art is a very good expression of any fandom. Whether it be DC or Marvel or Dark Horse. Some of the fan art found on the internet is awesome and funny. I remember seeing this one piece where Superman kills The Joker, and Batman is trying to stop him while saying you just killed my job.
Fan art has become even more popular since the arrival of social media. People share tons of this stuff on sites like tumblr, pinterest etc. A lot of artists draw exceptionally good stuff at comic cons as well. Comic cons are great places to see fan art.