To download all the wallpapers in your computer, simply follow the procedure below:
Open the terminal, copy and run following command and wait for some time.
bash
mkdir metis-brandings
cd metis-brandings
for (( w=1; w<=4; w++ ))
do
curl -LOS "https://raw.githubusercontent.com/metis-os/metis-wallpapers/main/metis-backgrounds-branding/files/$(printf b-%0.3d.jpg "$w")"
done
It will download all 4 branding wallpapers in metis-brandings directory.