A codebind isn't really necessary for this - it can be done via
Javascript added to the Master Page.

But what can I write in java script? Could you show example code?

There are a couple simple ways I can think of:

1) Use an "animated gif" to do the rotation entirely within a
single image file - some examples at
www.htmlgoodies.com/.../3479881
but you'll get a ton of examples from your favorite search engine for
"animated gif create". This doesn't require any master  page change,
just a new site  image.

2) Use some javascript in the master page  to rotate among different
image files - one example at
javascript.internet.com/.../...-image-rotator.html
but a ton more examples by searching for "rotating image javascript"