It’s only pasta sauce missing! 
Not just ugly, but downright unprofessional! I’ve said this before, but when I show Rhino to my coworkers, they think it’s a toy because it looks like a toy (then again, Rhino lacks so many basic things compared to other CAD packages, so maybe the icons are just honest).
(I’m redrawing most of the icons because I can’t stand them, but unfortunately only the main toolbar icons can be customized right now, none of the sidebar panels can and they contain some of the worst offenders.)