I'm trying to do a simple background image on a page in my SlimPHP web app.
In my CSS file (which is loaded fine) I have:
.image1 {
  background-color: transparent; 
  background: url("image1.jpg");
}
and my structure is:
-- project
  -- app
  -- routes
  -- templates
  -- www
    -- css
      -- stylesheet.css
      -- image1.jpg
    -- js
    -- i
      -- image1.jpg
In the network tab I get 403 Forbidden because slim is trying to access it as a page.
I have tried a few variations such as background-image, "../i/image1.jpg", but always get the same issues.
I can't find any other questions anywhere like this so there must be something simple I am missing!
I know SlimPHP fairly well but do not have much experience in CSS so any help would be appreciated!
Thanks
Additional:
Example of page request:
$app = new \Slim\Slim(array(
    'templates.path' => '../templates',
));
$app->container->singleton('log', function () {
    $log = new \Monolog\Logger('slim-skeleton');
    $log->pushHandler(new \Monolog\Handler\StreamHandler('../logs/app.log', \Monolog\Logger::DEBUG));
    return $log;
});
$app->view(new \Slim\Views\Twig());
$app->view->parserOptions = array(
    'charset' => 'utf-8',
    'cache' => realpath('../templates/cache'),
    'auto_reload' => true,
    'strict_variables' => false,
    'autoescape' => true
);
$app->view->parserExtensions = array(new \Slim\Views\TwigExtension());
// Twig
$loader = new Twig_Loader_Filesystem(dirname(dirname(__FILE__)) . '/templates');
$twig = new Twig_Environment($loader);
/**
 * Default home page
 */
$app->get('/', function() use ($app) {
    $app->redirect('/home');
});
/**
 * Index page
 */
$app->get('/home', function() use ($app, $twig) {
    $params['page_title'] = 'home';
    $template = $twig->loadTemplate('routes/index.html.twig');
    $template->display($params);
});
