Demo 3 - Apple-like Image Slider
This gives you another example which shows how the thumbnails can be easily customized.
The hovered thumbnail style is achieved simply through a background image:
#thumbs .thumb-on {background-image: url(active-bg.png);}
Source Code
The source code is included in the "Download" link in the page Menucool Javascript Image Slider.
Many Thumbnails
If there are many thumbnails and the containing block does not have enough room to show them, you can make the slider work together with Menucool jQuery Slider. See jQuery Slideshow.