cortina software package provides Wallpaper changer for gnome, you can install in your Debian 7 (Wheezy) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install cortina
cortina is installed in your system.
Make ensure the cortina package were installed using the commands given below,
$ sudo dpkg-query -l | grep cortina *
You will get with cortina package name, version, architecture and description in a table
| Distro | Debian 7 wheezy |
| Section | GNOME |
| Package | cortina |
| Version | 0.7.3-1 |
| Description | Wallpaper changer for gnome |
| Sub Section | GNOME |