I recently found Jon Schindehette's Art Order blog - a daily blog on the ins and outs of being an art director and how it relates to being an artist/illustrator. Aside from just fantastic insider information that you would normally have to kill for, or at least wait until an event of some kind to get, Jon also runs a weekly concept contest called "Concept Tuesday." A lot of fun with open entry, the artwork featured there every week (and well, almost everyday) is just jaw dropping.
The first challenge I entered was to take one of the existing D&D race (artist's choice) and move it ahead 4000 years. I chose the dragonborn.