Thanks for your reply, but that's not exactly what i'm looking for.
I would like to present thumbnails from the pictures on a page, like it is allready integrated in the gallery. But when i click on that thumbnail to view the bigger picture, i need to navigate manually through the pictures in the lightbox-box. And here is where i would like to have the slideshow option (like in the example linked).
I'm in the process of overhauling the UI plugins for ImageGallery. The idea is that you'll be able to integrate any lightbox or slideshow plugin your like with just a few lines of code. That will make it possible for you to integrate the lightbox example you're referring to. I don't have an estimated timeframe right now, but hopefully sometime this week.