Concept Sketch: Inventor's Assistant

A test sketch I made for the idea I had for the Goblins vs Gnomes contest. Unfortunately I have almost no experience with color in photoshop, and only 7 or 8 days left to enter a piece, during which time I'm going to be pretty busy with a trip to new york, so I wouldn't give myself very good odds for submitting a finished colored piece on time. Was fun to see how my idea looked on paper, though, so to speak.