I get big icons on my desktop after upgrading Ubuntu 16.10 (like 4 icon columns for height) How can I decrease icon size? Where is it? I use GT740M and all was OK with 16.04.
With Nautilus, use the top right icon (mozaic), then you will find a cursor to modify the size of your icons (desktop and Nautilus). The smallest is not that small... With 16.04 it was possible to reduce the size (i.e. 66%) in nautilus preferences, but this changed with 16.10. Neither dconf-editor nor Unity tweak tools offer tools to do this.
You might have accidentally zoomed in on your desktop post-install. Fortunately, this is a relatively easy fix.
To restore zoom back to normal, use the keyboard shortcut Ctrl+0. You can use Ctrl++ and Ctrl+- to also zoom in and out in more precise increments if you like.