Prevent the pleroma background from getting overwritten during upgrades

src/freedombone-utils-gnusocialtools

     fi
 
     if [ -f ~/freedombone/img/backgrounds/${gnusocial_type}.jpg ]; then
-        cp ~/freedombone/img/backgrounds/${gnusocial_type}.jpg $basedir/static/bg.jpg
+        cp ~/freedombone/img/backgrounds/${gnusocial_type}.jpg $basedir/static/bg_custom.jpg
+        sed -i "s|\"background\":.*|\"background\": \"/static/bg_custom.jpg\",|g" $basedir/static/config.json
     else
         if [ -f /home/$MY_USERNAME/freedombone/img/backgrounds/${gnusocial_type}.jpg ]; then
-            cp /home/$MY_USERNAME/freedombone/img/backgrounds/${gnusocial_type}.jpg $basedir/static/bg.jpg
+            cp /home/$MY_USERNAME/freedombone/img/backgrounds/${gnusocial_type}.jpg $basedir/static/bg_custom.jpg
+            sed -i "s|\"background\":.*|\"background\": \"/static/bg_custom.jpg\",|g" $basedir/static/config.json
         fi
     fi
 }