How can I install the Faenza icons for Libreoffice on 14.04?

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:

sudo apt-get install libreoffice-style-sifr

To chose this icon set, then go to Tools > Options > LibreOffice > View and then select "Sifr" under "Icon size and style" drop-down.

[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.]

1. Download the icon pack from http://dfiles.eu/files/k2dq3mwkq

2. Go to the directory in which you downloaded it, right-click on the zip file and choose "extract here"

3. Navigate in the just extracted folder to "LibreOffice Pack Icons-0.3.8-a-1/LibreOffice 4.1.0 (Sidebar)/Faenza icons LibreOffice 4.1.0"

4. Open a terminal and type sudo nautilus /usr/share/libreoffice/share/config/

5. In the Nautilus window that opens rename images_crystal.zip to something like images_crystal.zip_old and keep the Nautilus windows open.

6. Copy the images_crystal.zip file from the Faenza icons LibreOffice 4.1.0 folder you have kept open and paste it in the windows displaying /usr/share/libreoffice/share/config/.

7. Close nautilus and open LibreOffice.

8. In LibreOffice choose Tools/Options/View, then select Crystal as the icon style and voila: