Implement Slideshow With Too Many Images?

I have written a javascript slideshow with pause-play-next-previous buttons, but the images are too many and users have to wait too long especially with slower connections - i wonder if anybody can suggest a way to implement the script with fast preloading of the first few images, increment preloading or a similar trick. I will copy my code below but i also copy first this link:

[URL]

which is an example of increment loading slideshow working fine! javascript and i wouldnt know how to customize it in order to take away the link function, that i dont need, and add captions and buttons etc.

I do know some jquery plugin could do but i am trying to go more into the code, even though i still need a lot of advices and tutorials, the goal is solving this specific problem but also learning! Thx a lot in advance.

Here my code (just 2 images here in the list to make it shorter for you, the complete list is more than 50 pics!):

<script language="JavaScript">
<!--
var interval = 8000;
var random_display = 0;
var imageDir = "portraits/";

[Code].....