Ok thanks to your message I found a solution which works for me in nautilus 3.x. In dconf-editor, modify
thumbnail-size, located in org->gnome->nautilus->icon-view
I set it to 128 and it is now exactly like the "make it more compact" option I used to love in nautilus/gnome 2.x!
I don't know if this is what you were looking for, but for me there is almost no space left between my icons and using my favorite thumbnailer program; "cover thumbnailer". It is simply ace!
Cheese, thanks for the idea of using a gnome editor!