There should be an option to change the default icons (example in picture below) server-side so when the icons are edited, everybody should be able to see it. It shouldn't impact loading of the server since they're only 16x16. I noticed that the TeamSpeak 3 icons (the ones in the picture) are merged with the actual GUI of TeamSpeak. They should be separated to achieve being able to change the icons in my picture, server-side. As for the OverWolf part, I think we should be able to disabled the icon on clients server-side.
It's little features like these that a lot of people like.