Sexual reproduction basically outsources some of the selection effort to the cognitive apparatus of the species itself, thereby introducing a massive amount of additional selection signals (mainly by the much increased necessity to model other minds, namely minds of the opposite sex). Many of these signals promote traits that are useful for survival (mainly intelligence and health).
Your point about physical features made me think of how physical attractiveness plays into human development as well.
Research has shown that beauty in humans is defined as physical symmetry. So "novelty" in our case might be defined as someone who is really ugly - the elephant man.
So in this case, beauty wouldn't really fit into the robot walking example as it's neither fitness (moving the foot forward) or novelty. More a different type of fitness that increases the odds of reproduction.