How can I delete from my smartphone the images downloaded by Google Chrome from the internet, which I can't find anywhere?
In the folder /data/data/com.android.chrome and its subfolders, would be the place to look. You will need superuser permission to be able to access this folder. In Total Commander start File System Root.
For example /data/data/com.android.chrome/cache/image_cache Has picture files. Actually all the files in there are pics even though they have no extension.