Tweet App.net is a great service that allows to create a great looking landing page for your app, whether it is an iOS, Android, BlackBerry, Windows Phone 7, or HTML based mobile web apps. The process is fairly easy and flexible, and the results are really awesome.
A new feature from App.net enable Facebook integration to help you showcase your App directly from your Facebook page. The page tab showcases your app with high-resolution screenshots displayed within the actual phone or mobile device. You can easily add a Like-gating option in case you want to set this tab as a 'welcome tab' and have people liking the page before using it. Also, if you choose so, the Facebook tab integration can automatically posts news stories to your timeline. You’ll have the option to post a news story to your timeline when: Your app is updated in the app store, or your app goes on sale.
So how does this work?
First you'll need to create a landing page for your app (it is free for one app + facebook integration). Just follow the steps (add logo, banner, colors, etc), and once you complete with the page settings, you will have the ability to easily integrate the App.net page you just created on your Facebook page (you'll find a link to that on the app dashboard, under the applications tab)
Here's an example of how it can look on Facebook (there are many layout to choose from)
But wait, there's more, you can also customize the 'Tab Icon' of your App:
Click on the 'Edit' option in the corner of the tab icon; then on 'Edit Settings'; then you'll have the the option to upload a new photo under 'Custom Tab Image' - Make sure the new icon photo you upload is at the size of 111 x 74 pixels.
If you already moved to the new Facebook Timeline Page, then you probably need a new alternative to the old welcome page. Start with App.net - so far it's the best solution I've tried.