The question says it all. I had a working icon set on LibreOffice 4.1 that got messed up due to an upgrade to 14.04.
How can I install my Faenza icons again?
[Note: because icons are for the Desktop users (and not server users), the following steps use as little terminal as possible. For noobs: nautilus is the standard file manager.]
You can get the Sifr icon set (very similar to the Faenza set depicted in another answer):
Much more simply by using the PPA available for Ubuntu 14.04:
To chose this icon set, then go to