Currently LibreOffice uses Metro style system icons which look ugly. You have much better looking icons in the main LibreOffice launcher menu. It would be nice to be able to choose which system icons are applied to executable files. I would like to have better looking icons on my taskbar and on my desktop. This metro style is going nowhere. Nobody likes it. It looks primitive and flat. You already have better looking icons in the launcher. I'm sure users would be pleased to be able to switch through options menu to those more elaborate icons which you use in the launcher.
On Windows the project's Quickstarter and Desktop/Taskbar/Jump List icons were changed at 6.3 from our 'legacy' Tango based icon theme to the new Windows 10 compliant Colibre icons. 6.2.8 is well past EOL, 6.3.4 will rolling out soon, while 6.4.0 is in late beta. Please update or at the least install in parallel to test.