Thumbnail generation with nginx reverse proxy
that is similar to me, i added this line in my nginx vhost config, 

location ~* /sites/default/files/styles/ {
    if (!-e $request_filename) {
    rewrite  ^/(.*)$  /index.php?q=$1  last;
    break;
    }
}


you need to reload to make the image display, hope someone can improve my answer