Get/set gnome wallpaper from terminal/cli

gsettings get org.gnome.desktop.background picture-uri
gsettings set org.gnome.desktop.background picture-uri 'file:///home/andrew/Pictures/Fz6D1KDaUAAKbN7.jpeg'

Also you can set xml file for animation:
path: ‘file:///usr/share/backgrounds/contest/lunar.xml’

<background>
  <starttime>
    <year>2009</year>
    <month>08</month>
    <day>04</day>
    <hour>00</hour>
    <minute>00</minute>
    <second>00</second>
  </starttime>
<!-- This animation will start at midnight. -->
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/Startrail_by_Hajime_Mizuno.jpg</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/Startrail_by_Hajime_Mizuno.jpg</from>
    <to>/usr/share/backgrounds/Copper_Mountain_by_Eduardo_Battaglia.jpg</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/Copper_Mountain_by_Eduardo_Battaglia.jpg</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/Copper_Mountain_by_Eduardo_Battaglia.jpg</from>
    <to>/usr/share/backgrounds/Warm_Filament_by_Eduardo_Battaglia.jpg</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/Warm_Filament_by_Eduardo_Battaglia.jpg</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/Warm_Filament_by_Eduardo_Battaglia.jpg</from>
    <to>/usr/share/backgrounds/Multiverse_by_Emanuele_Santoro.png</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/Multiverse_by_Emanuele_Santoro.png</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/Multiverse_by_Emanuele_Santoro.png</from>
    <to>/usr/share/backgrounds/winter-is-leaving_by_Gixo-dark.png</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/winter-is-leaving_by_Gixo-dark.png</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/winter-is-leaving_by_Gixo-dark.png</from>
    <to>/usr/share/backgrounds/Lunar-lobster-side_by_Gixo-light.png</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/Lunar-lobster-side_by_Gixo-light.png</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/Lunar-lobster-side_by_Gixo-light.png</from>
    <to>/usr/share/backgrounds/Lobster_Wallpaper_Grey.png</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/Lobster_Wallpaper_Grey.png</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/Lobster_Wallpaper_Grey.png</from>
    <to>/usr/share/backgrounds/winter-is-leaving_by_Gixo-light.png</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/winter-is-leaving_by_Gixo-light.png</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/winter-is-leaving_by_Gixo-light.png</from>
    <to>/usr/share/backgrounds/LunarCatcher_by_Espio347.png</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/LunarCatcher_by_Espio347.png</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/LunarCatcher_by_Espio347.png</from>
    <to>/usr/share/backgrounds/Lunar-lobster-side_by_Gixo-dark.png</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/Lunar-lobster-side_by_Gixo-dark.png</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/Lunar-lobster-side_by_Gixo-dark.png</from>
    <to>/usr/share/backgrounds/Flow_by_Emanuele_Santoro.png</to>
  </transition>
  <static>
    <duration>1795.0</duration>
    <file>/usr/share/backgrounds/Flow_by_Emanuele_Santoro.png</file>
  </static>
  <transition>
    <duration>5.0</duration>
    <from>/usr/share/backgrounds/Flow_by_Emanuele_Santoro.png</from>
    <to>/usr/share/backgrounds/Startrail_by_Hajime_Mizuno.jpg</to>
  </transition>
</background>