So, A quick tour of the new Taskmanager Customize Icon feature.
A few notes:
1) Only available when desktop lookup has been successful or there is a Launcher. (The goal is for desktop lookup to work, so I'll treat failures as bugs instead of changing this requirement... at least for now).
2) Available through context menu. Taskmanager is diverging from the standard drag and drop an icon file mode. With good reasons, This will keep the drag and drop of files into a launcher sane (the application is invoked with those files).
3) I think icon issues should be dealt with in the installed icon theme. But as we know there are always egregiously ugly misses with icon themes and not everyone has the knowledge/time/rights/inclination to modify their chosen icon theme. So we have this.