According to the LibreOffice 5.0 Release Notes, we will have a new icon theme by KDE, Breeze. But, I can’t seem to find it?
I want to install it on my Ubuntu 14.04 Trusty Tahr.
You can find the package in the standard repositories.
sudo apt-get install libreoffice-style-breeze
Then, restart LibreOffice and go to Tools > Options > LibreOffice > View. Select Breeze from the Icon size and style drop down box towards the left, and then click OK.