Background image rotator

I'm not looking to reinvent the wheel here, but I'm willing to learn if someone can point me in the right direction...I'm trying to make a page with a rotating -background- image that is reasonably easy to update. It just has to work in firefox, just for personal use and all.

I'm really not looking to become an expert in this stuff, nor am I asking for someone to just hand me the code; a reference of some sort would be brilliant, something where I can understand the different approaches and what the code means and which technique is best for me would be great :). There seem to be so many options for making an image rotator thingy that I'm just kinda confused, and there doesn't seem to be much out there for making it work for a background image specifically :\. And a lot of places just say "cut and paste this and it will work" without 'splaining what exactly it's doing.

Oh, and I'd like the image to change on refresh, not a slideshow type of image rotator, and I don't need fancy transition effects or anything.

You know what would be really cool actually...well no, I'm getting ahead of myself...but...ooh, what I would -really- like is to have something that rotates the entire stylesheet on refresh, not just the background image. *raises eyebrows* I -think- that's possible, no? If it's not than the background image dealie would make me happy beyond belief *grins*.