Nginx error page static content not loaded

Running Nginx 1.4.1 I have the following config to display a custom error page in case my backend messes up. The page is displayed but custom fonts & images are not loaded.
My custom error page (50x.html) is in /usr/share/nginx/html/. Static contents in subfolders img & fonts.

From my browser I can see that the static contents url is append to my current url which makes them unavailable. For instance if I'm browsing www.domain.com/user/account, Nginx will try to load content from the server :

URL 
/user/account/img/logo.png
/user/account/img/main.jpg
/user/account/img/footer.png
/user/account/fonts/miso-regular-webfont.ttf

Instead of from sr/share/nginx/html/img/

Here is the configuration portion :

error_page 324 500 502 503 504 /50x.html;
        location = /50x.html {
                root /usr/share/nginx/html;
                allow all;
                internal;
    }

Thanks for you lights.

EDIT 1 :

Thanks Alexey, path are now corrects but images still not displayed. At first backend failure, Nginx tries to fetch images from Apache whereas Nginx should serves the whole maintenance page and not relies on the backend. Why this behavior ?
When a backen goes sick I can't rely on it, even for a maintenance page.

Thank you.