Canadian concept artist Aaron St. Goddard has done illustration, concept design, storyboards and matte painting for companies like Piazo Publishing (who seems to have taken over Dungeon and Dragon magazines from TSR), Darrel Brown Media, Radical Entertainment and Mainframe Entertainment. (Mainframe is responsible for my all-time favorite 3-D CGI TV show, Reboot.)
St. Goddard’s site showcases his designs for environments and characters (like the hazard-suited character above left), but the stars of his oeuvre are his nicely scary creatures (like the minotaur above right).
The site also features a step-through (not exactly a tutorial) of his coloring process and promises a similar feature for his drawing process in the near future.
St Goddard seems to work primarily digitally, drawing and painting his characters and environments in Photoshop. He also works in 3-D applications.
His approach is generally one of color-filled linework, rendered far enough to give a relatively finished painted appearance. This gives his exotic creatures and wild characters a degree of realism while keeping the loose feeling of a drawing.
There is a brief interview with him on Animation Arena.