How do I get the scene to load in the background when on the loading screen?

Hi Guys
I have a loading screen where in the scene i have an image sequence showing but i have to put a 10 second delay on loading the level so it show all of them because after the 10 seconds everything stops whilst the level loads.
How do i get it so the level is loading in the background whilst the images are showing.

This is my loading screen code:

var seconds : float;

var levelToLoad : String;

function Start() {	
	yield new WaitForSeconds(seconds);
	OpenLevel(levelToLoad);
}

function Update () {
	if(Input.GetKeyUp(KeyCode.Return) || 
		Input.GetKeyUp(KeyCode.KeypadEnter)){
	OpenLevel(levelToLoad);
	}
}

function OpenLevel(level : String){
	Application.LoadLevel("DemoLevel");
}

If you have pro:

Otherwise you could try have the loading screen using DontDestroyOnLoad so it remains while the other scene is loading; then have a method in the demolevel (maybe on Awake?) to destroy the loading screen picture?

ok i’ve had another go at this and i can use ASinc but it stops my animation, i want my animation to continue until the level is loaded and then change scenes.
Any ideas please???