How to serve the image files using express framework in node.js?

In my application im using express framework to serve the client side files.But while giving background image for the html element.Its showing failed to load given url.

var express = require('express')
    , http  = require('http');

var app = express();
app.configure(function(){
    app.use(express.static(__dirname + '/public'));
});
var server = http.createServer(app);
var io = require('socket.io').listen(server);
server.listen(8000);

In public folder i have created javascripts,stylesheets,images folder.Now i'm getting javascripts and stylesheets.But i don't know how to access the image file.

.logo {
    background:url('localhost:8080\logo.jpg');//This image url not loading
    float:left;
    width:20px
    height:20px;
}