Hello,
I am running OMERO 5.4.10 on Ubuntu 16.04 with nginx 1.10.3
I had started OMERO.server with the command: OMERO.server/bin/omero admin start
And OMERO.web had been configured with:
"OMERO.server/bin/omero config set omero.web.application_server wsgi-tcp"
And the nginx configuration generated with 
OMERO.server/bin/omero web config nginx --http "$WEBPORT" > OMERO.server/etc/nginx/omero-nginx.conf
When I try to run nginx with the following command:
/usr/sbin/nginx -c /opt/omero/OMERO.server/etc/nginx/conf/omero-nginx.conf
I get the error: 
nginx: [emerg] "upstream" directive is not allowed here in /opt/omero/OMERO.server/etc/nginx/conf/omero-nginx.conf:1
contents of omero-nginx.conf:
upstream omeroweb {
    server 127.0.0.1:4080 fail_timeout=0;
}
server {
    listen 8881;
    server_name $hostname;
    sendfile on;
    client_max_body_size 0;
    # maintenance page serve from here
    location @maintenance {
        root /opt/omero/OMERO.server/etc/templates/error;
        try_files $uri /maintainance.html =502;
    }
    # weblitz django apps serve media from here
    location /static {
        alias /opt/omero/OMERO.server/lib/python/omeroweb/static;
    }
    location @proxy_to_app {
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;
        proxy_buffering off;
        proxy_pass http://omeroweb;
    }
    location / {
        error_page 502 @maintenance;
        # checks for static file, if not found proxy to app
        try_files $uri @proxy_to_app;
    }
}
			
		
    
