Aside from the powdercoat and ano, I've noticed that a large factor in "robot beauty" is continuity in design style. You can look at a 148 robot without the black coating and you'll be able to tell it's a Robowrangler machine solely based on how its design style fits that of the Robowranglers (and all the nonagons in the metal). Most teams with "aesthetically pleasing" robots have developed their own design style over the years that sets them apart from the rest. There were two shiny blue robots in the finals of the Central Valley regional, but they could clearly differentiated from each other solely on how their design styles were (and the fact that one wasn't moving ).