The Internet Speculative Fiction Database credits him with cover art for about 500 book and magazine covers published since 1994[1] Nielsen is best known[citation needed] for his work on projects such as Star Wars, The X-Files, Chronicles of Narnia among many projects including advertising campaigns, designs, and magazines.
Feature articles focusing on his work appear in design publications and fanzine magazines.
Nielsen has been an international speaker on digital art and has served as a judge for the Society of Illustrators[citation needed] and a variety of professional illustration award programs.
In 1995, the husband-and-wife team of Cliff and Terese Nielsen (since divorced) collaborated on Ruins, a Marvel Comics mini-series[2] (two issues).
[4] Besides this, he was known for working in the magazine Carpe Noctem, and was interviewed as well as created a few covers.