I am using the latest version, 18, and I found the info here:
http://www.opera.com/help/tutorials/intro/customize/#customspeeddial

I don't see/have the wrench tool o.O How can I get it?

"Customize Speed Dial
You can tailor Speed Dial to suit your needs by changing the layout, background and more, as explained below:

Change the Speed Dial background
Display Speed Dial and select the Configure button * at the top-right of the window."