LibreOffice includes several icon sets (those that live in the project, and developed as part of it): Breeze, Colibre, Elementary, Karasa Jaga, Sifr, Tango. Any of them is available to be chosen on OptionsLibreOfficeViewIcon style (on Linux, distros may split the icon sets to different packages, and allow to install them separately, so the installed set may not include all of them).