Have the options for icon size changed after it forked from OpenOffice? In Openoffice on my Maverick netbook I can reduce the size under Tools > Options > OpenOffice.org [probably LibreOffice now] > View. It sounds strange that they would remove the feature from LibreOffice.
If it's missing, you should probably file a bug with LibreOffice.
Apparently, scalable icons are used in the menubars for Ubuntu 15.04. The FS Icon set specifies a minimum value for the scalable icons as 257 pixels. The solution is to set the minimum value appropriately, so the icons can be scaled down to the required size.
sudo sed -i "s|MinSize=|MinSize=8\n#MinSize=|g" /usr/share/icons/fs-icons-ubuntu*/index.theme
In the above command, change /usr/share/icons
to the location where you have installed your FS Icon set.
Additionally, in order to fix the icon sizes in Gedit, follow the steps outlined in the following question, since the fix still applies to Ubuntu 15.04.
How to use 22 pixel size icons for toolbars in Ubuntu 14.04
Note that fs-icons-ubuntu-mono-dark were used in these screen shots, but this solution will fix all of the icons included in the FS Icons set.
Here is what Nautilus looks like after applying the fix.
Here is what Gedit looks like after applying the fix.
Best Answer
To configure the layout of the application icons in the GNOME Shell, you have to modify
/usr/share/gnome-shell/theme/gnome-shell.css
. Note that the contents of this file may vary as it is dependent on the particular theme that you are using. In the case of the Dark Glass theme, here are the modifications necessary to reduce the size and layout of the displayed icons by 50% in Applications Overview.Read more here.