You can see 3 concept pieces from NS half-way down the list of pieces. Somewhere around 30 down. Here is an excerpt from the article:
"One of the most unique and common forms of art on the Internet these days is called concept art. Concept art is a form of illustration where the main goal is to convey a visual representation of a design, idea, and/or mood for use in movies, video games, animation, or comic books before it is put into the final product..."