RefineryCMS - images not working properly

In my app with RefineryCMS I'm having problems with images - it uploads fine and available by url like:

http://localhost:3000/system/images/W1siZiIsIjIwMTUvMDkvMTQvMTRfMzJfNTVfOTEyXzIuanBnIl1d/2.jpg

The problem is on refinery admin panel and on site fails with 502 error. As I understand refinery images transforming images for thumbnails with help of imagemagick and trying to display it on the site.

I'm using refinerycms 1.0.9, unicorn as webserver and nginx as http server

my example nginx config for site:

server {
    listen         80;
    server_name example.com
    root           /home/deploy/example/current/public;
    charset        UTF-8;
    access_log   /var/log/nginx/example-access.log;
    error_log   /var/log/nginx/example-error.log;

    try_files $uri @unicorn;
    server_tokens  off;

    location @unicorn {
        proxy_pass        http://unix:/home/deploy/example/shared/unicorn.sock;
        proxy_redirect    off;
        proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header  Host $http_host;
        proxy_connect_timeout       1200;
        proxy_send_timeout          1200;
        proxy_read_timeout          1200;
        send_timeout                1200;
    }
    location /system/images { 
        proxy_pass http://unix:/home/deploy/example/shared/unicorn.sock;
        proxy_cache dragonfly; 
        proxy_cache_valid      200  30d; 
    } 

}

my custom config for refinery images:

require 'dragonfly'

app = Dragonfly[:refinery_images]

app.configure_with(:imagemagick)

app.configure do |c|
  c.convert_command = "/usr/local/bin/convert"
  c.identify_command = "/usr/local/bin/identify"
end

How can I solve the problem and display images?

Thanks