Choose Options, View, Icon size and style.
If large set was selected, choose Small.
No changes occur.
To have change, I must choose another set of icons (example : crystal), then return to first style.
So the sizes list has no effects but if the style changes.
Can confirm on LibreOffice Master (3.6), circa January 10, 2012, Linux x86-64.
*** This bug has been marked as a duplicate of bug 35972 ***