luna-user@lunauser-System-Product-Name:~$ sudo apt-get install wallpaper-plug
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  wallpaper-plug
0 upgraded, 1 newly installed, 0 to remove and 3 not upgraded.
1 not fully installed or removed.
Need to get 0 B/1,928 B of archives.
After this operation, 26.6 kB of additional disk space will be used.
Selecting previously unselected package wallpaper-plug.
(Reading database ... 165540 files and directories currently installed.)
Unpacking wallpaper-plug (from .../wallpaper-plug_0.1-0~18~precise1_i386.deb) ...
Setting up elementary-default-settings (0.4.3-0~25~precise1) ...
ln: failed to create symbolic link `/etc/skel/.config/plank/theme': File exists
dpkg: error processing elementary-default-settings (--configure):
 subprocess installed post-installation script returned error exit status 1
Setting up wallpaper-plug (0.1-0~18~precise1) ...
Errors were encountered while processing:
 elementary-default-settings
E: Sub-process /usr/bin/dpkg returned an error code (1)