How to use custom background picture in Ubuntu 13.10?

There area several ways built-in to Ubuntu 13.10. Though it is curious that your screen shots look far different than mine.

Option 1: right click the desktop and select 'Change Desktop background'

Click on the '+' button to bring up a dialog box to select an image

or

Select 'Pictures Folder' from the drop down to select an image in your pictures folder

Option 2: Open an image in IMage Viewer. Right click somewhere on the image and select 'Set as Wallpaper'.

Option 3: Find an image using Firefox. Right click on it and select 'Set As Desktop Background'

Try Variety

Installing Variety

• open terminal with CTRL+ALT+T and execute these commands to add repository and install it.

  sudo add-apt-repository ppa:peterlevi/ppa
  sudo apt-get update
  sudo apt-get install variety
  

• Then open variety from Dash

• And get started to dig a lot of features. The more you dig the more features and wallpaper you'll get.

_{Source: peterlevi.com/variety/}

Install dconf-tools with:

sudo apt-get install dconf-tools

In the dash type dconf and start the dconf-editor. Select org -> gnome -> desktop -> background and change the value of picture-uri with the file you want.

Syntax:

file://<full_name_of_the_image_file>

Here's a visual aid for this:

Or open the image file with any image viewer, right click on the image and select Set as Desktop Background.