I imagine there is a setting for that but I cannot find it...
I think you can't do it with configurations but you can recompile nautilus with your own icon size (and it's not too complicated). I've compiled it 5 minutes ago and this was the first time I compiled a thing from ubuntu, but it worked, so you can do it, too.
Here is a nice How-To, i did it this way with nautilus 3.4.2 (only difference: the line to change is line 369, i searched for "pixbuf = nautilus_icon", the value to change the icon size is icon_size)
For example I changed it to 5, so the icons are very small
with new size: