I came across this set of imagery on Fun Guerilla in a piece titled "The Most Beautiful Robots Anyone Would Like to Date". The image sets arent well attributed unfortunately, but there are some very cool pieces, photos robotiscised for us. Some of them are pretty arty, though interestingly they steer clear of the face, keeping it human. Here are a couple of the pics munged together, but the reason I am posting it here is that the logic of this sort of image manipulation can be a powerful tool for concept sketching. Taking a character or look from somewhere and adapting it to the specifics of the character being designed can be emotive in some extra dimensions when compared to the from-scratch work.
[Images via FunGuerilla]