Random + fading + preloadbar gallery/bacgkround change

[LEFT]Hi, I have to code asap, a fading, random, with preloader photogallery. It would be used as a background random change, the thing is that I need that the previous images stays in screen while preloading the following and the transition should be betwewn images.(should notbe able see white in transitions) the random may not me a problem, I can forget about that.
Also, is there a way to list with numbers, the pictures that will be loaded, or add a next prvious button?

Well is kind of tricky, but if anyone knows some tutorial or has any, it would be great to have a look, cause everything I can find will not show any image while preloading the next one (could be also cool to see a loadbar).

well, thanks to all.