One thing that drives me nuts about lightbox is the fact that the image has a margin of about 60px from the top of the page and then, large images go beyond the viewport, forcing one to scroll down.
Here's how you can somewhat customize this feature:
1. Open js/lightbox.js and look for var lightboxTop = arrayPageScroll[1] + (document.viewport.getHeight() / 10);
2. Comment the rest of the line as shown here: var lightboxTop = arrayPageScroll[1];// + (document.viewport.getHeight() / 10);
Voila! You can add a custom number of pixels say: "var lightboxTop = arrayPageScroll[1] + 10;" for the lightbox window to have a 10px margin from the top window.
MeasureIt