Properly stretching images to fit screen size with loadingURL

[MIKEYMASTALSKi]

I am a 100% complete PHP noob, so going to need detailed explanation.

I have a 1920x1080 image I'd like to use for my loading screen, currently it spans too far across my screen, or is way too small. Do I need different universal sizes and a script to select the appropriate size or is there a script that will automatically stretch to the appropriate size?

Any useful scripts for switching images also?

Thanks :v:

[landocalrissian]

Using css set the images width to 100% and height to 100%

<img src="background.png" style="width:100%;height:100%;position:absolute;top: 0;left: 0;" />

I assume by 'switching images' you mean a random image is shown each time?

[Chesnut]

Assuming it's the background image.

body {
background: url('background.jpg') center center no-repeat;
background-size: cover;
}