Wallpaper stretching over multiple monitors on Fedora 19 (Gnome 3)

Question

I'm running Fedora 19 (GNOME Shell 3.8.4). I have a dual monitor setup (two 1440 x 900), and I want to be able to stretch my wallpaper over the two monitors, like I was used to when using Ubuntu 12.04.

I don't want different wallpapers for each workspace, nor different wallpapers for each monitor (that would be pretty cool, but falls out of scope of the question). What I want is a 2880 x 900 (or any 3.2:1 proportional image) to be shown half on one monitor, and half on the other:

How I had set it on Ubuntu

If I boot with my 12.04 LiveUSB, it starts in "mirror displays" mode. I have to disable display mirroring (enable extended monitors) in order to have different images on each screen:

Then, I open the System Settings and on the Appearance section I can choose the background, and have several options. Chosing "span" (see the dialog on first image rightmost side) will have the background like I want it to be.

How I (don't) have it on Fedora

The System Setting screen doesn't have an "Appearance" icon, just a "Background" one, with no options at all. If I choose an image, it will be applied to each monitor repeatedly, like this:

Answer 1

I have no idea why the configuration option is not available in the gnome control panel but you can set this using dconf-editor.

Run dconf-editor from a terminal, navigate to org.gnome.desktop.background -> picture options and set it to spanned:

Answer 2

Installing gnome-tweak-tool lets you customize not only the wallpaper alignment, but other absent options such as enabling / disabling minimize and maximize buttons, showing icons on the desktop, changing the shell theme and colors, changing fonts and its options (size, hinting, etc).