The bug has been corrected in the version PHP 7.0.8-1~dotdeb+8.1.
After investigation, it appears that there is a bug in PHP-FPM 7.0.7.
Although the server Nginx configuration includes a root directive, pointing the root of WordPress, in the parameters passed to the php-fpm socket, the PHP scripts do not know this root and are unable to load images.
My environment : Debian Jessie, Nginx, PHP-FPM 7.0.7.
The wp-admin Medias bibliotheque do not show the images.
The url http://{addr}/wp-includes/images/uploader-icons.png is not found.
