I just put together this landing page template, the design is very popular especially  if your promoting a single product,  the background is set to no-repeat which gives it that steady effect. You can pretty much use any size background but my recommendation would be to use something under 1000px for a quick load time.

Im using bootstrap and font awesome for the social media button, but you can pretty add any elements from bootstrap/font awesome, so check them out.

I  included iPhone PSD with a smart object layer. Please see at help document on how to change the background image. See the demo below, and don’t forget to like TechAndAll on facebook