One of the best gaming series dating back to the NES era is Castlevania. I love the official artwork for the series, but I was curious of the artwork fans had produced. Here is some fan art I collected from Pixiv. Enjoy.
If you like Castlevania, check out the fan game:Koumajou Densetsu - Scarlet Symphony. It is a Tohou doujin title that uses the characters from that series in a 2-D action game similar to the more modern Castlevania games on DS. It is a cool PC game that you can buy fairly cheap online, and the artwork is simply amazing. I put a sample of the art below.
Here is a link for more information on this unique title:http://blog.hardcoregaming101.net/2009/08/koumajou-densetsu-scarlet-symphony.html.