If you are looking for a PHP server side solution read CSS Random Background Image Rotation.
- Enter the id value of the element you wish to apply the background to. For example, if you have a div element with an id value of wrapper, e.g, <div id=”wrapper”>, enter wrapper in the Element ID field.
- Enter either a relative path, or full URL to the image to be used for the background. For example, the logo for this site can be referenced as:
- /wp-content/themes/k2/styles/thoughtafter/sign.jpg a path relative to the root of this site, or
- http://www.somesite.com/images/imagename.jpg a full URL
Enter the path/URL value in the URL of image field. Click the add another image link to enter more images.
- Copy the complete generated script block and paste into the <head> section of your web page, immediately before the closing </head> tag.
If you have comments or feedback about this tool please leave them at this post.