The term robot makes me think of something that was built with a machine in mind, while the term automaton makes me think of something built with a person in mind. In fact, the mechanical props that are the characters for restaraunts like Chuck-E-Cheezes are called Automatons, and those from FNAF were initially tagged as such.
For some reason, somebody's gone and wiped those tags out, completely, from the whole five_nights_at_freddy* search list, though. I think it should be brought back, so that any character, such as the bulk of the robotic Bonnie, Freddy, Chica, and Foxy images, would be tagged as automaton, since they represent a real-world species, while those like R.O.B., Wall-E and Eve_(wall-e) could be tagged as Robot, since they resemble little more than a machine.
Updated by TheHuskyK9