This plugin may help point you in the right direction... Check out the fade option. Examples of how they work are at the bottom of the page http://jquery.malsup.com/cycle/
I actually have tried to use the cycle plugin. I just can't get it to work by changing 3 different body background css. The only background that appears is images/indonusa3.jpg. It works if I replace the js css code with (img src) but it only works for small image not full screen (body background).