Change Cover images from slideshow to one still image

Hi,

I'm hoping that someone could help me find a bit of code that will change the Cover page of my website from displaying all uploaded photos as a slideshow to selecting one random image and keeping it static. Ideally if the page could trawl existing galleries of photos for said image then it means I can upload a new collection of photos and know that they'll be included in the selection process if possible.

Thanks in advance for any help

I think the way to do this would be use a cover page with a default still image and then have a script that substitutes the default for a random image from a set of images uploaded to the static files area of the site.