Custom Post Layout

I need help in setting up a custom template.

I’m currently creating a site that enables users to upload an image with a limited amount of text. Once the image and title have been submitted, it will be saved as a post.

Once they have been submitted. They will go to gallery.

Now this is the piece of the puzzle I can’t code/figure out.

On selected pages, I want a randomised post that has a image big enough to fill the screen to appear as a background image and the title (which is the limited amount of text) to appear in a div I specify.

The problem I having is applying the php code to the background div and then separating the title into another div.

Hope it all makes sense.

A point in the right direction would be plenty