Как я могу программно обновлять обои?

Выше ответ для Ubuntu 16.04 64-бит больше не работает. Задача на sudo dpkg -i libidl0_0.8.14-1_amd64.deb:

john@Laptop:~/Software/Kompozer$ sudo dpkg -i libidl0_0.8.14-1_amd64.deb
[sudo] password for john: 
Selecting previously unselected package libidl0:amd64.
(Reading database ... 366612 files and directories currently installed.)
Preparing to unpack libidl0_0.8.14-1_amd64.deb ...
Unpacking libidl0:amd64 (0.8.14-1) ...
Replaced by files in installed package libidl-2-0:amd64 (0.8.14-4) ...
dpkg: dependency problems prevent configuration of libidl0:amd64:
 libidl-2-0:amd64 (0.8.14-4) breaks libidl0 (<< 0.8.14-3) and is installed.
  Version of libidl0:amd64 to be configured is 0.8.14-1.

dpkg: error processing package libidl0:amd64 (--install):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 libidl0:amd64

Решена:

sudo apt-get -f install
sudo apt-get remove libidl-2-0
sudo dpkg -i libidl0_0.8.14-1_amd64.deb

и затем, как и раньше,