To add an icon to the dash you can make custom icons and put them into
Simply copy and paste this template into gedit (or another text editor) and save it as
libreoffice.desktop into the folder.
If you want it so the icon is available for all users, put the
.desktop file in
The Categories=Office bit means it will show up under "Office" in the dash. If the icon is in
/usr/share/pixmaps/libreoffice.png then actually you can just write
Icon=libreoffice, there's no need for the full path, but only if it's in that path. Don't know if that works in Gnome 3 though.
If you have translations for the language you can specify them using something like the following:
And replace [en_GB] with the code for each language.